Be full out on count one
Your team already has the hardware.
Down Beatz is a team broadcast app for colorguard and marching arts competition warm-up. A coach broadcasts voice to the team's phones and Bluetooth earbuds, with synced competition music, section channels, a broadcast metronome, and a warm-up timer — with no special hardware beyond phones, earbuds, and a portable router.
Contact: downbeatzapp@gmail.com