Is there a tool that will give you a better indication of wireless signal strength than…?

 If you're running a Windows machine, then Marius Milner's NetStumbler is probably your best bet. The latest version runs on only WinXP and 2000 but supports many more wireless cards than before. There's also a "ministumbler" version for PocketPC. It's free, but you'll probably find it so useful that you should consider making a donation to support Marius' work.