I was looking at this thread from @zvirus and it got me thinking.
I have a power bank designed for 9v effects pedals but it has gone hooey on me. Still charges, holds its charge and I can still run pedals from it. But the led which indicates it is charging, turned on, or when power gets low has failed. So I can use it no problem, just charge it up night before I need it and I'm good to go. But it would be good to know when it's fully charged without reaching for the multi meter, or to know it's on, or off. Would it be possible to plug something like @zvirus has made into one of the outputs and have it light up when power get's too low, or come on when power is full and go off when it reaches a certain level (which might be better)? It has two outputs so using ne for this would be fine.