I've used my mini traxion with good results, though the toothed-cam makes me a little nervous. I imagine taking a dynamic fall with incomplete engagement of the cam resulting in a torn sheath or severed rope.
I used Billygoat's "Yates Rocker" and thought it was ideal for solo top-roping. Fed smoother than the minitraxion, no teeth on the cam, very small and inconspicuous. Since then I've kept my eye out for one, but they seem to be hard to find.