and power off? You need some sort of motion sensor...
"hidden cameras" use power... whether battery operated or plugged into the wall. The "battery" could alos be one of these <http://www.amazon.com/Xantrex-852-2000-XPower-Powerpack-Portable/dp/B000E6LEIC/ref=pd_bbs_sr_1/104-2287151-1773507?ie=UTF8&s=automotive&qid=1182658782&sr=8-1>.
The links throughout this post are not advertisements for any particular product or vendor - merely examples of various products.
Ideally, the surveillance camera <http://www.amazon.com/s/ref=nb_ss_gw/104-2287151-1773507?url=search-alias%3Daps&field-keywords=security+camera&Go.x=0&Go.y=0&Go=Go> video is connected (wired or wirelesly) to a DVR like <http://www.amazon.com/Lorex-Channel-Digital-Video-Recorder/dp/B000BX1WDA/ref=sr_1_7/104-2287151-1773507?ie=UTF8&s=electronics&qid=1182658931&sr=8-7>. This particular unit has a hard drive - and you set the motion detection areas that cause the recording to go from 1 every 4 seconds to real time for a specified amount of time. The 250 gig internal drive can hold up to about 20-30 days of surveillance if it is not always real-time... and that is with 4 cameras. If you have only 1 camera, it the hard drive will last longer... but I don't know how long the portable battery power will last.
At some point, you would take the DVR somewhere to connect to a TV and playback whatever it captured.
FYI, if you get a night-cam, the infrared emmiters are visible in the camera when it is dark.
There is no "camcorder" that will do what you want without you being there.
I have a horse barn that I would like to watch what happens when I'm not around. There are other horse/owners who use the same stable. I fear that there is something going on and I wanna catch them in the act.
is there a way to record ( with a hidden camera ) to a card or something that could be taken out and viewed later?? There is no electric in the barn.. and it's in the next town over. 20 miles away.