SeekDroid is a one-time fee if you just want the basic functions of locating and remote wiping your phone. I used to use it before I got hooked up with the Device Policy thing. I would say it's worth the few dollars they charge.
I've been running the open-source
Prey Project. It's all about trying to track your lost gear. I don't think it supports remote wiping, but it does have all sorts of other things, like GPS tracking.
Another tracker that seems to be highly regarded is
Cerberus, which does seem to have a remote wipe feature, among other things. I haven't played with it myself, but the pricing (one time EUR 2.99) seems pretty reasonable.