If you want multiple audio sources mixed into one feed, you'll need either a passive or active mixer. Several years ago I purchased a MixIt2
MixIt2 that does this and it works pretty good. The only problem I have with the unit are the 3.5mm audio connectors (sometimes they aren't seated correctly and the audio isn't piped correctly). From the MixIt2 you can plug in a wiRevo
wiRevo that will turn the 3.5mm audio source to a BT signal. You then pair the wiRevo to your BT headset/helmet. I use this setup on the HP2S sans the mixer since I only want the V1 audio on the 2s.