I did consider an arduino on the car itself to control the motor and servos wih an RF serial module (you get speed control that way as well – as it is its just stop/go with the opto hack – you can use pwm and a transistor+capacitor for smoothing to control the cars motor speed) but would have been overkill for what I was trying to demontrate and I couldnt build it for under £50! but if you do want to go the whole hog and build from scratch there are plenty of robot kits out there for arduino.
I found a chassis on ebay that looked quite decent:
http://www.ebay.co.uk/itm/Arduino-Duemi ... 27bf012f3a
The scope of the remote hack I did was to demontrate a prototype of Microsoft Kinect controlling a remote rover for a local schools technology project, so finesse of the RC car wasnt a huge issue+cost had to be low. It just had to go left right back and forth with serial commands from a c# program and the kinect sdk. For the web cam viewer I used the VLC activeX plugin on the c# form to recieve and display the wifi camera stream – again had the PI been on the car it would have broadened the available protocols for streaming and perhaps added some stability control+AI for autonomous control.
Also in the event I ended up slowing the car down by cutting the positive wire on the cars motor and popping a resistor on as it was too fast in its standard form!
In terms of tracing the connections on the buttons of the remote all you need is a multi meter set to test continuity and place the probes on the back of the button on the controller. If there is no continuity when the button isnt pressed and continuity when it is, you just found your solder points! – takes about 10 seconds a button plus a minute to solder on the cat5 wires per button.
Overall the Pi will be golden for projects like this as an onboard Computer simply because it enables so many options in terms of control, AI, logic, Communications and sensors (3d camera would be awesome!)that an arduino alone simply cannot do + the cost is very similar. Basically the difference between a fully fledged computer and a MCU designed for simple HW control.
Another idea for RC control is some higher end RC transmitters have USB built in, perhaps thats an option?
And I know I mention Arduino alot, however I do see alot of the work done with Arduino porting well to the Raspberry and then moving to greater levels of functionality/integration as many of the ways hardware is interfaced/created on an Arduino will port very well to the RPi effectively creating a nice ready-made cookbook of projects to be adapted/improved on! Although one rule of engineering I have stuck by over the years is to keep things as simple and too the point as possible, its great to have X,Y,Z extra functionality and future proofed with insight to the hilt however the core idea needs to be solid, reliable and easy to maintain/support the rest is just ancillary especially with open source projects. You dont need to build in obsolecence, fail points, apps or consumables, its just got to work well and reliably Thats why I like the whole open source hardware scene - want an app? theres not a fee for that