Well, I might suggest that you can put yourself out there for hire as a programmer/developer, though I'm not sure what kind of market exists.
You could also build something based upon Arduino and sell that. Though we as tinkerers forget it, you really don't lose that many sales to hobbyists. Just because a few folks might be willing to build their own based upon your published design or code, it actually usually takes a fair amount of effort and dedication to do so.. enough that it's prohibitive for a consumer product. Let's say you invent a toy based on Arduino and publish the code and design as open source.. especially at the outset, it may be a selling point that it's "Arduino Inside.."
I'd also recommend becoming very well versed in embedded programming in general, this is a market which has a very bright employment future as more and more products become "intelligent". See the recent thread on a microcontroller-driven paper shredder that is out there on the market (and not even touted as "smart", it's just a shredder); companies will be looking for experienced embedded systems developers for some time to come...