Applications? mix several parallel effects together (split with y cables then blend back together), feedback looping (2 in 2 out could achieve this), splitting signal to low input impedance effects (like some fuzzes in parallel) etc. Personally i built one for myself to mix 3 looping pedals together.
Runs on 9v dc. No battery space inside. Text is engraved and pedal is powder coated. Not available right now but maybe soon.