Hmmmmm... Ignition controlled hot wire... like, say, the cigarette lighter? I tapped into mine for just that (since I don't use it much anyway). Simple to do, especially once you take apart the dash as if you were removing your stereo. Like a five minute job. Two screws and everything else just pops off. Check out the tech section on my web site for detailed instructions...
Usually the cig. lighter circuit is about 20 amps. Cig. Lighters draw alot of current to get hot. As long as the Valentine 1 and the laptop don't draw more than 20 amps, you should be fine. I wouldn't think they would draw anywhere near 20 amps. Worst thing that could happen is you blow a fuse, then you know not to run both together, but I think it should be fine.
(I think 20A should be sufficient to run a 27" tv and a VCR BTW)