If you ever watched my review of the DroneKeeper Mini before, then this is the same thing - but what they've done is remove the in-built lithium battery to get around the problem they had with shipping (only FedEx would carry it and the shipping became ridiculous)
Pretty expensive, but if you've ever wondered around and around a field for hours on end looking for a quad - then it feels less so
! No longer available (http://www.youtube.com/watch?v=SuygRGZHeno#)
I picked up from the comments in YouTube that there's another similar product coming from HellGateFPV called the buzzer - which I think it a similar thing, but looks like it will be carried by a UK shop as well. Which sounds cool, I'll attempt to grab one to test.
I think that HellGate one looks like a far better idea in so far as you can install it and then forget all about it. Having this extra thing to remember to do before each flight just means that the time you forget will almost certainly be the time you really needed it.
Swings and roundabouts IMO. The Hellgate one is cool, because it replaces the normal buzzer and you don't have to do anything, but of you have a bunch of quads you fly (which isn't just me, there's lots of you with 4 or 5) then you need to buy a buzzer for each, but the DroneKeeper you can move across.
We shall see, the HellgateFPV guys have completely sold out of their first production run, but are aiming to send me one of the first of the next run.
Well it shouldn't be beyond anyone with the skills to put a quad together to install it with a connector so that it could be swapped about just as easily. But I'd just forget to do that so the optimal one for me will be the ones you can get from Banggood in a few months that'll be a buzzer, LED board and have a small battery to do this as well and it'll cost about £6.59