Could you give the name/link to that device please? Sounds good.I am using one that I put on my helmet or on my passenger's one. There are several good points:
1) it is possible to ride several bikes with the same benefit, it is not located on one bike.
2) as the light and brake light of this device are at the view (hight) of any car driver, you are seen.
3) very easy to charge (micro USB), 8 hours of work, adjustment of sensitivity with your phone, you do not feel it on the hard hat, ....
I started to use this kind of light device as my wife and I were down with the bike two times, as "follower" cars did not want to stop behind us at a "STOP" signal.