I think you are not going to find such a device, because the usage case is just really weird. Maybe it exists but generally BT is not intended for communication that is nore than a couple meters away, and all devices that use BT as a protocol are intended for pairing to a host device that is doing the work. Normally any case where people are communicating they are, or have a chance of being, far enough away that a different RF protocol than BT is more apprpriate.
A market already exists for headsets and similar things that are for exactly your purpose. Its just not based on BT.
Even if you could find such a device, it seems very easy that you would lose connection with one another while single track biking.
