My friend and I bought units early in the summer. They are very good in bike to bike performance. It makes longer rides more fun and safer, as each rider looks out for the other (road hazards, gravel on curves, stopping traffic, etc). It is very small and easy to put on any helmut and easy to connect with your phone and gps. Battery life depends on usage, but 7 to 8 hours is typical with moderate usage. I highly recommend these devices. A new model was just introduced with longer mic boom (better for full face helmuts) and an auxillary mp3 plugin. This is definitely the "best for the money".