I started six varieties of peppers on Saturday using this method. For a heat source, I left them on top of my direct tv box in the a/v cabinet -- the things stays warm all day even when not in use -- I'm sure it sucks a lot of power too.
Anyway, two of my varieties (Key West Hybrid and Spanish Spice) saw 100% germination after just four days, so I guess the temperature is just about right with that setup. I also kept the ziplock bag inside a towel for insulation.
I've kept to using coffee filters instead of paper towels because I read somewhere that there is less of a problem with the roots digging into the paper. Is that right?
Another 1 1/2 weeks and the tomato seeds go in!