In Computer Science Mobility is the ability to use technology on the go whilst providing access to information or applications from portable, networked computing devices i.e. a Mobile Phone.
A good example of mobility is the ever decreasing size of mobile phones. What was once considered to be a "mobile phone" was one that had to be literally carried around in a vehicle. Step forward a couple of years to the "transportable" phone, which freed the user from their vehicle but weighed about twenty pounds. With the arrival of so called "brick" phones in the mid-1980's came the era of "portable" phones. This continuing decrease in size and weight of handsets has greatly increased the mobility of mobile phone users today. Currently over 900,000 mobile phones are sold every three days. 
The first proper mobile phones were manufactured by Motorola from 1983 to 1994. They were part of a series called the Dyna-TAC series which stands for Dynamic Adaptive Total Area Coverage. Previous to this Motorola had being producing mobile phones for vehicles which were very heavy and almost impossible to power. A guy called Martin Cooper at Motorola and his team produced the DynaTAC8000x, the first mobile phone small enough to be carried around. The DynaTAC's retail price of $3,995 was a very high price to pay for a mobile phone but by the time Mitchell retired in1998, mobile phones and their accessories made up two thirds of Motorola's $30 billion in revenue. 
The DynaTAC 8000 Series consisted of a display with red LEDs, the DynaTAC International Series with green LEDs, and the DynaTAC 6000XL used a Vacuum Fluorescent Display. These displays were limited in what information they could show. The battery availability was for a call up to 60 minutes, after this you had to charge the battery for anything up to ten hours .
The spec for the DynaTac 8000 was as follows:
Input type: 12-key / numeric.
Dimensions: 13 inches (h) 1.75 inches (w) 3.5 inches (d). 
The DynaTAC Series was succeeded by the MicroTAC Series in 1989.
The MicroTAC was released by Motorola in April 1989. It was a smaller and lighter phone than anything previous. It was a "sleek" flip phone and was designed to fit into your pocket. They had a black an 8-character dot-matrix red LED display, which allowed the user to view more information on screen than the Motorola DynaTAC 8000X. The phone also had a built-in alpha-numeric phone book which was a big feature for its time. Other features of this series included GSM, Bluetooth, 2MP and microSD Slots. 
These days almost every handset has a camera. The first phone to have a built in camera was the Sharp J-SH04, which was introduced to the Japanese market in 2001.
All of these phones are in contrast to today's generation. The most popular and sought after mobile phone today is known as the Apple iPhone. The iPhone is a line of Internet- and multimedia-enabled smart phones designed and marketed by Apple Inc. The iPhone functions as a camera phone, a portable media player, and an Internet client with e-mail, web browsing, and Wi-Fi connectivity using the phone's multi-touch screen to provide a virtual keyboard in lieu of a physical keyboard.
Software Advances in the 90's
During the 90's mobile phones started to revolutionise quite rapidly with new phones constantly trying to out do older models. A major revolution was the ability to send a text message on the mobile phone. This happened for the first time in 1993. At first text messaging was slow to take off with customers in 1995 sending on average only 0.4 messages per GSM customer per month.  This might have been due to the fact that charging systems were not really in place at no-one knew the true cost of sending a text. The first SMS message was sent over the Vodafone GSM network in the UK in December 1992. The text read "Merry Christmas". In contrast to where we are today, with over 4.1 Trillion SMS text messages sent in 2008. SMS is a massive industry today with up to 2008, SMS alone had produced over 81 billion dollars globally. 
In 1994 IBM and BellSouth teamed up to produce the first Smart Phone known as the IBM Simon. The Simon had the power to send and receive faxes, a pager function, and the features of a PDA. It even came with games and had a touch screen. It cost a whopping $899.
The Nokia 5110 was a very popular phone of the 90's. It was one of the first mobile phones to have a game which was called Snake. It was also the first phone to feature an interchangeable faceplate, allowing you to alter the design of your phone to make it look "cool". I think everyone at some stage had one of these phones.
The Nokia 7110 was the first mobile phone to contain an application called WAP. WAP is a web browsing application. Obviously it was not as advanced as the mobile web browsers of today, but it was a big step into greater connectivity and interactivity.
The Nokia 3210 was the first mobile phone to have a built in antenna. By adapting an internal antenna, the Nokia 3210 looked better in appearance without having to forfeit anything in terms of reception. The Nokia 3210 was also the first phone with T9 predictive text. 
The first generation of mobile phone networks was known as 1G. 1G networks used analogue circuit-switched technology, with Frequency Division Multiple Access. It used 800-900 MHz frequency bands. The networks had a low traffic capacity, unreliable handover, poor voice quality, and poor security.
The second generation of cellular networks was known as 2G. 2G networks were the next stage in the development of wireless systems after 1G. 2G used a mobile phone system that used only digital technology. The demands placed on the networks, especially in larger populated areas, meant that stronger and more powerful methods had to be employed to handle the large number of calls to avoid the risks of drop offs in communication. 1G and 2G networks both use the same cell structure but there are differences in the way the signals are handled. 1G network's are not capable of providing the more advanced features of the 2G systems, such as caller identity and text messaging.
The third generation 3G is where most network providers are today in terms of coverage and bandwidth. 3G networks allows for higher data rates. 3G networks allow network operators to offer users a wider range of advanced services. 3G also allows them to achieve more network capacity. 3G networks offer more security than 2G. With the increased bandwidth and location information available to 3G it allows for applications that were not previously available to mobile phone users. These applications include:
Mobile TV - a provider redirects a TV channel directly to the subscriber's phone where it can be watched.
Video on demand - a provider sends a movie to the subscriber's phone.
Video conferencing - users can see each other when talking.
Tele-medicine - a medical provider which provides advice to the potentially isolated user.
Where we are today and the future?
4G is the fourth generation of cellular wireless standards which is in development at the moment. It aims to provide a wide range of data rates of gigabit-speed. 4G is being developed to adhere to the QoS and rate requirements set by existing 3G applications like wireless broadband access, Multimedia Messaging Service, video chat, mobile TV, but also new services like HDTV content, minimal services like voice and data, and other services that utilize bandwidth.