Although, "hey great idea".... any thinking of this mod should bare in mind the effects of magnetic fields on electronics. I have not seen a disassembled Pronto so this really is only a possibility not fact. However the magnets that apierre is suggesting are quite strong. One of basic rules of working circuit boards is not to use magnetic tools. The fields they produce when passing through any type of metal strip, (wire/circuit board trace) will induce a current into the strip. (A.K.A generator action)
Worse yet..... On board flash memory can be effected by magnetic fields. I not saying it will physically damage components, but can easily corrupt data being stored.
What I'm getting at is. If the magnet being used moves at all while installed, (movement would be necessary). There is the possibility that a current could be produced that may have negative effects. This might corrupt your installed pcf and firmware. I am not aware if the Pronto processor has any burnt root programming. Something that isn't effected by firmware updates. If there is, that could also be effected, and may not have a readily available fix.
Sorry... I don't mean to be so negative, but people should be aware of the possibilites before attempting this mod.
Best of Luck...!
....Light travels faster than sound. That's why some people appear bright until you hear them speak.