Ok I did this with the right parts in about 10 minutes. Very simple.
You need to buy an Arduino. http://www.arduino.cc/
And either a Wifi Shield or an Xbee Shield. Let me explain in simple terms. The Arduino was designed to have small boards plugged into it. These boards can actually stack on top of each other. Such boards are called SHIELDS. So in simple terms, if you want to communicate using bluetooth, you need to buy a bluetooth shield. If you need GPS and GPRS, you need to find a GPS/GPRS shield. If you need both, you buy both and stack them on top of each other.
Now I mentions Xbee... http://en.wikipedia.org/wiki/XBee
Xbee is actually a TX / RX Device which is easily programmed using the XBEE software.
An Arduino can be programmed using a language called Processing (its actually a sub set of Java... meanings its identical to Java but with limited features).
Recommended Shopping List:
2. Xbee Shield (this is just a board)
3. Xbee Module (the actual transmitter and receiver)
You must make a lot of reading too because I cannot possible tell you everything here but for example Arduino is open source, meaning there are many different sizes, shapes and uses for Arduino as everyone can make his own. For example a lillypad is an arduino on a circular board which can be implanted into your jacket or whatever crazy idea you want to think of.
Also Xbee there are 2 versions. Version 1 has a different use the Version 2... I would go for Version 2 as its slightly more complex, but the main purpose is to make a MESH http://en.wikipedia.org/wiki/Mesh_networking
which is your case.
Any ways Good luck and do a lot of reading.