You know, that beater car of yours would be infinitely cooler if it had a push button ignition. Fortunately, HAL 9000 from instructables has put together a comprehensive step-by step guide that teaches you how to install one. If you have some skills with a soldering iron and a basic knowledge of the equipment involved, it should only take you a few hours to set up.
The only drawback (besides the possibility of screwing up your ignition) is that you need to have the key in the "engine on" position for this hack to work. It won't start the car, but it kind of defeats the whole purpose. However, some security measures are necessary given the fact that a unprotected push button ignition would make your car super easy to steal. There are workarounds for this, although most of them would still result in increased vehicle vulnerability. [instructables]