Ozzy now does directed retrieval.
How these things happen is interesting: For every 'non-standard' trick or exercise I have always found that the dog and I actually teach each other and sort of work out what we're trying to do: In Ozzy's case, it's this (so far, he's so smart that more is inevitable); Kiki will pick up anything off the floor and hand it to me (this is SERIOUSLY useful); Ava has a fairly large repertoire; Tuli would "smile" on command; Tahr, my first dog, could jump and pull things from my mouth (it started with roses). Hogan would snarl ferociously on command, leap into my lap, and he also had a large repertoire.
I never set out to teach any of these things; they just sort of happened, but the process in which both sets of lights (human and dog) go on and an understanding is clearly reached is one of the best things in life. I find that sort of communication addictive, which is really why I train. The what is generally less important than the how and wow.