Signal Strength Mode is working!  The RSSI data comes back in the passive scan for devices as an integer. Based on what I found from a quick google search the following is the 4 color scale I used for this new mode:

>= -70  STRONG  Green
-70 to -85 GOOD  Yellow
-86 to -100 FAIR  Orange
< 100 POOR  Red

I should probably call this disco mode. I should be pretty awesome with a full grid of devices represented. Next is going to be adding a button to switch between modes.