I've not considered those, as this is the first I've ever heard of such a thing, however, I don't think I can afford the $700. I'm wondering if I'd need to replace the crank at all with something like the white industries DOS ENO 2-speed.

So I had an idea and i was hoping to get some feedback on feasibility from y'all. I was wondering if it would be possible to add a second, larger diameter cog to the RadRunner1 for going uphill, I'm ok with getting off and manually moving the chain as well. Like old school tour de france before derailleurs were invented.