I have installed a Belkin fm modulator into a clients car. He had reasons similar to yours and had to go the route of an FM modulator.
The Belkin is not a hard-wired fm modulator, but rather a wireless broadcasting one. You can select ANY station you want to broadcast to. The little screen on the modulator is back lit. The modulator can run off two tripple-A batteries, or has a car lighter power adaptor.
It works but maybe a little too well. It interferred with the clients Nextel cell phone. They were unable to make or receive calls. It apparently blocked their signal. Also when the modulator senses no audio, it shuts off. It kicks back in when there's audio again, but it's rather annoying. It also picks up a substantial amount of interference.
We just installed a hard wired Jensen FM modulator. If you need a model number, PM me and I'll post it here. The Jensen works perfectly. It patches through the head unit's antenna, and has jumpers on the modulator to set what station you want to use it with. As a note, any fm modulator will suck when using an inverter in your car. We are using a dc power supply and there is little background noise with the Jensen Mod.
For carputing, I highly recommend the Jensen, and do not recommend the Belkin wireless.