Sensing Movements while Moving
The sensor in the phone/watch detects acceleration. That's why FlickStart wants you to put a bit of snap into a move before it recognises the move.
If you are standing still on the ground then the signals from the sensor are all based on how you move the device. But if you are traveling somewhere (walking, in a car, in a plane, etc.), the signals are a mixture of what is happening to your body as a result of the travel along with how you move the device.
FlickStart tries to sort out the device movements from the overall movement but won't be able to make the distinction all the time. For instance, if you are on a bike and go over a speed bump, FlickStart might see that as an 'Up' movement depending on how fast moves are meant to be and your speed over the bump. The range of accepted movement speed is controled by the slider on the 'MOVEMENT' tab. The force of movement introduced by bumps also may trigger movements. Again the slider for move strength may provide some isolation from such bumps.
In general though, you can expect FlickStart to have a harder time recognizing moves while the phone and watch are in motion. Jiggling caused by walking and running will have a worse effect than cruising in a car.
Changing Move Types to Suit
The type of travel you do makes certain movements more likely to happen by accident. For instance when running with an AndroidWear watch moves like 'Back', 'Forward' and possibly 'Left' and 'Right' are likely to happen just as a result of your normal arm action. So you probably would not set up commands which are triggered by such movements, rather you would use rotations and perhaps 'Up' and 'Down'.
If you use a command set like the music player commands under a variety of scenarios (sitting, walking, running, driving) you can copy the basic command set once for each scenario and adjust the 'Flick type' in each copy to suit the scenario.
In situations like riding a bike or driving where you want minimal distractions, FlickStart gives you a chance to do an action without changing your grip or your line of sight.
Nonetheless, you should practice FlickStart movements in quiet places before venturing into traffic!