- P2P lending algorithm, like ripple?
This, hardcore. If P2P won't work, centralize it, and allow loans/repayments via SMS as well
Other ideas:
- A simple, open-source Windows, Linux and Mac app that simply reads the wallet file you drag to it, and spits out a text file containing all the private keys
- Convert the C++ blockchain parser (thread
here) into a nice, shiny, easy-to-use program that lets you pore over, examine, chart, etc. the data as much as you like
- Another lite open-source Android app (that works well) couldn't hurt. I'd download it.
- A "sweep" app for smartphones. Someone hands you a QR-code of a private key, you scan it, and the app collects all the unspent outputs and bundles them into one transaction sent to your default receiving address. All with one or two clicks for speed. (Optional: allow a "power-user" mode where you can scan multiple codes, choose which unspent outputs to spend, decide on transaction fee, split the amount across multiple receiving addresses, etc.)
- A (good!) strategy game where you can spend BTC to upgrade, and put up BTC competitively (you win, you earn his BTC, and vice-versa)
I'd pledge varying modest amounts of BTC to see any of the above get done.