I can give you the advice to NOT buy a wireless one, have not seen one that works worth a darn.
I ended up with a super cheap $15 license plate mount camera off amazon, has been working for a little over a year now so far, though I have it only powered on reverse, it shouldn't be hard to power it with a switch so you can select when you want it on, or perhaps power it on with your running lights, lots of possibilities. I would buy a separate long video cable for it too, most of them include cables that are a bit too short for most trucks, I think most have smaller cars in mind.
I view mine on my aftermarket radio, but you can easily use a separate cheap $15 LCD monitor to view it too.