First of all a car had to be chosen. To justify the name 'Megacar', which I think is a slight bit over the top and mainly explainable by the youth and the slightly excessive nature of the project leader Kim Schmitz, the car was not supposed to be a normal automobile available to the masses, but nothing less than a 'Brabus 5.8'. This car is based on the new Mercedes S500, but its engine is increased to 5.8 liter, thus providing 400 bhp. The Brabus 5.8 has no speed limitation and reaches a high speed of 170 mph, it has a modified suspension, special interior, four television/video screens, a S-VHS video recorder, DVD-player and many more things. The price of the base car makes 'Megacar' unfortunately already unaffordable to 99.999% of the people.
That's what it looks like, the 'megaCar'.
The 'phones' used inside the car are 16 GSM-modules, using the European/Asian digital mobile phone standard that's today also found in several places in the US, e.g. the San Francisco Bay Area, where it's called 'PCS'.
In this picture you can see the 16 GSM-modules and the Cyclades Z-Box above it.
Those 16 modules are connected to a GSM-booster, which distributes those 16 aerial-connections to two physical aerials on the roof of the car, providing a send/receive-power of 2W to each of the GSM-modules.
Instead of the reserve tire, you find the GSM-booster and an additional battery.