On my Eris, I have:
- WiFi Analyzer (farproc) v2.2.8
- WiFinder (pgmsoft.com) v 1.5
- wardrive (Raffaele Ragni) v ?? * (* not the current version in Market)
All of these work as advertised (without force closes) on my Eris.
Between WiFinder and WiFi Analyzer, I tend to use the latter. (Now that I think of it, I'll probably uninstall WiFinder).
The channel graph in WiFi Analyzer is useful both for determining what networks are nearby, and their relative strengths... but also for deciding if you should move your home WiFi router to a different channel.
The wardrive app is pretty good for, well... war driving. It can generate .KML files for viewing later in Google Earth. (Or push them to your own Google Maps).
HTH
eu1