If you've got some patience, you might wait for the Splitter Gear 2cam to come out - http://www.splittergear.com. I've climbed on them a few times....
IMHO, They're pretty comparable to aliens in terms of size, range, action. The big difference is that they need probably *half* the crack profile of the comparable alien size. In other words, if you need say a 1 inch long crack to fit an alien, you can fit a 2cam in about half that.
Disclaimer: the developers are friends of mine, and I'm an investor in the company. YMMV...
Myke
