This is a wonderful passive AB-Y box. With this, you can send your signal to two sources (one or the other, or both at the same time) OR the opposite - two signals sent to one amp/pedal. The battery in this pedal is only for the lights - you can remove the battery if you wish and the pedal will still work.
Be warned - this is a passive splitter box. You may experience hum or ground loops if you use two amps which are not on the same ground/earth. In the testing stages, this was used with two amplifiers with no added hum at all. However, it should be noted that the building had no earthed sockets. Fancy a punt?