this is the verbiage from the manual which led me to believe that the 106 will do scanning and stalk in background :
Signal Stalker II Object (STLK)
A Signal Stalker Object (STLK) stores the parameters
necessary for the radio to rapidly sweep a range
of frequencies for strong signals from nearby
transmitters. A STLK object can be used for
standalone operation—the radio just sweeps and
stops when activity is detected, or for stalking that
is performed while the radio is scanning. During
scanning, the radio will check for activity on all the
enabled Scannable Objects: TGRP objects, CONV
objects, LMIT objects and STLK objects
This is from the radio reference wiki. You have to have Signal Stalker 1 to do that and Pro-106 has signal stalker 2
Signal Stalker II
Signal Stalker II allows you to watch for activity on all band frequencies or Police/Fire frequencies only. You can also turn on/off frequency sub-bands using the corresponding number keys.
Signal Stalker II will not work in the background like Signal Stalker I or Close Call.
Once an active frequency is found, the transmission is played through your scanner’s speaker, and you can quickly store it in any of your scanner’s memory locations.
Signal Stalker II functions by rapidly sweeping through the RF spectrum in 1 MHz segments. If RF signal energy is detected in a 1 MHz segment, Signal Stalker II will sweep through the 1 MHz segment in finer steps until the source of the RF signal energy is found.
You can change the normal Signal Stalker II operation to the Special Signal Stalker II operation. If you lock out 5 frequencies within a 1 MHz segment, the scanner will skip that segment in subsequent sweeps.
Available on the Pro-2054, Pro-97, Pro-2055, Pro-163, Pro-164, Pro-106, and the Pro-197.
You can program a scan list to do Signal stalker everytime it cycles thru the frequencies. Press Program, new, srch, then stlk this will program signal stalker into a scan list. I would choose an empty scanlist to program it in case you want to disable it you can do it fast. Everytime it scans it will do signal stalker scan or search also.