Can anyone recomend a good magnet switch, the kind where you need to place a magnet on the switch to open/close the circuit?

 

Depends on what you need it for.

You can get some very small glass reed switches at RadioShack that you can use as hidden switches just about anywhere (under panels, head liner, etc). Good for a valet switch replacement - put a small magnet in the cap of a pen and keep it in the vehicle.

DEI makes two magnetic switches that are especially good as a replacement for hood/trunk pins. One model is very small and is hard-wired NC, the other is slightly larger, but let you wire it as NC or NO. They are models 8600 and 8601 respectively.

I use the small one in place of a hood pin and on the fuel filler door (it's sealed so there is no issue of sparking). They're better than hood pins in every way imaginable, and can be placed under the wiper cowl with a very small painted rare earth magnet on the underside of the hood to make it completely invisible.

 

I need one where I can carry the magnet on my keys and have it go for a metal or glass panel to work the switch. I'm having a hard time finding a good switch, so I'm thinking of rigging something up.