1. I run mine off my ACC...I also ran a hidden on/off switch under my seat so that I can use it in Illegal States...I just hit the switch if I get pulled over and tell the officer that its not wired up...
2. Most older radar detectors need a straight and clear line of site. My old whistler was very picky about what was blocking it (ie things hanging from rearview mirror). If you just want to see if a cop is directly infront of you...than it may work.
My advice though is to just buy a GOOD radar detector. Old or middle range ones arent gonna do you any good in Ohio. Your state troopers have some high tech equipment. The better one you have, the less likely you are to get pulled over. As long as they are legal, you cant get in trouble for it. Ive been pulled over a number of times and forgot to take it down (I usually do while the cop is picking his nose wasting my time)...it was just buzzing away while the cop wrote the ticket infront of me

. When Im ****ed (usually for getting an impropper lane change ticket), I turn up the volume and really annoy em.
I got my first detector 6 years ago and am yet to get one stolen...I always leave it on my dash...Check out
http://www.radartest.com for some NON-CAR&DRIVER tests.
Try one of these if you have the cash. The day I buy a sports car is the day I buy this...
http://www.escortradar.com/srx.htm