This is something most of us would love to have, and is not a novel idea, one has to wonder if it is in any way practical as if it were it should be everywhere already. I have played with the idea a bit, and had practically zero success, but I am certainly not the best person for the job.
20ma is all I can glean from the specs? 7 - 20V? that at best is .4 watts, not exactly a stellar hi fi number.
Before blowing 45 euros I would want to hear from someone who actually tried out the product......
Mmmmm, disregard everything I have said:
What a great idea, don't delay, get one today.