There are all sorts of wireless video setups available. Check http://www.x-10.com for some.
I imagine batteries would be a real pain to tote around.
For greater range, you could use a "repeater" type setup (not HAM repeaters).
'Course - eveything would just go to the spot you left.... :-0
Super Circuits.com has a few video/audio setups, but they're expensive. The only one I saw that would be feasible was around $1,500, but it had a 3 mile range. It would less expensive to just buy one of the 12vdc surveliance VCRs and hook a PIR and camera up to it. Put it in a waterproof case and bury it somewhere in the woods.