We have a BVS Panther drive test analyzer. We purchansed it because it does 40 lamba averaging with the addition of M/A-Com Typhon software. I haven't been too impressed with the quality of the hardware, and they aren't cheap. The other vendor that comes to mind is
http://www.surveytech.com/.
Do you intend to take automated, continuous measurements, or do you intend to manually take the readings?
Like you, I've been trying to come up with a better way for basic drive testing. It seems simple enough, all you basically need to collect is the RSSI and lat & long. Map programs like Delorme or Streets & Trips have data import features that allow you to map the data. The M/A-Com M7100 will display RSSI in dBm, and the control head data is RS485. This can be converted to RS232 and fed into a laptop. Someday I intend to get our software engineer to throw together a little program to grab the RSSI values out of the string and throw it in a file with a location. In my mythical "spare time"....
Good Luck!