The effects of fading loss from building reflections can also cause momentary dropouts with any RF signal and momentary RSSI would be useful if it measures SNR rather than actual carrier level.
For Wifi, the dynamic range can easily span from -40 dBm to -100 dBm, with a threshold in -70 to -80dBm range that affects bit-rate.
There is a free software tool for Windows, called NetStumbler which is extremely useful for WiFi testing. When doing fringe signal reception diagnosis it has a time chart display in dBm and an audio beacon. It works with all leading WiFi chipsets and I found it extremely useful for antenna pointing optimization because of the wide range in Friis Loss and Ricean Fading dropouts, which becomes dominant due to reflection nulling. On numerous occasions I found a way to improve reception from routers > 50m away and sometimes less inside buildings with just a slight change of 1 degree or 1mm of the position of a dongle or laptop to make the difference between >=54Mbps or it auto-negotiating and equalizing at b speeds well below 11Mbps.
However satellite signals are very weak to begin with. The vertical propagation loss is huge and typically acceptable Rx levels vary from -160dbW to -185dBW depending on location and antenna.
However, here are 3 classes of Rx's which generally fall into 3 ranges of sensitivity > -172dBW, > -180dBW, > -190dBW.
The algorithms and integration times strongly affect the Rx threshold and tracking errors, which are tradeoffs. So I would expect RSSI to be useful in areas like a forrest under wet leaves or tracking Ricean fading downtown in highrise areas, but not generally an acceptable way to compare performance of chipsets. It would be useful in field trials with such fading losses from antenna gain, ground plane effects and orientation.
There is also poor correlation in methods of RSSI measurement between chipsets as there is no standard. When I analyzed this in the ISM band in the 90's for co-channel interference thresholds, I used an Integrate and dump method over the baud interval, rather than peak or average or some other method. In some cases, min level is more important for dropout detection.
Most operating system give a false indication of signal strength in 5 bars and has very poor correlation with RSSI . I would expect similar poor correlation withsignal strength on GPS units that display this and it may include other factors such as error rate or jitter. On OSX I found once, it only indicated channel speed rather than actual signal level.
These devices all have RSSI but , I don't know their chipset brand or part number(p/n).