If you are a long-time user of Apple products, their switch to the Lightening connector probably left you with orphaned 30-pin connector devices, like iPhone/iPad powered speaker docks. Well, this handy $15 adapter will turn those into useful Bluetooth speakers! (Even if you still live in the 30-pin world, this would be a great thing to get.)
I just got one and it works great. The only caveat is that the dock must be one that charged your iPhone/iPad, since the adapter requires a power source.