If you use a Bluetooth heart rate monitor, the burnt calories are calculated using your heart rate, age, weight et cetera. And the activity level is calculated using the calories. Thus, using a heart rate monitor does influence the activity level.
I use a Polar watch for heartrate monitoring. And I also have my android with RunGPS, tracking my route and stuff. I would not like to give up my Polar, so easy to check HR when exersising. BUT I also would like to have HR monitored in RunGPS. Can't have both, I know. How would activitylevel behive if I started to use a bluetooth belt. Feels it is at low level now, too low.