The PRO-83 (and 2051 BCT-8 clone) is made by Uniden for RadioShack and has Signal Stalker I (Close Call in Unidenese) and has a quick *near field* detect over a wide frequency range or band selected range. You activate it by pressing Func + the Signal Stalker symbol for >2 seconds. You can cycle through Signal Stalker only, Signal Stalker + Scan, with backlight flash and, or beep alert.
The PRO-97/2055 has Signal Stalker II and is manufactured by GRE. You can select the band or multiple bands to "stalk" and it works fairly well with stong near feild signals, but will only work as a stand alone feature. I do like the second Signal Stalker II mode that includes only Fire frequencies or Police Frequencies, that is a plus when on the road.