How about something that tells you the value of your points/miles if you were to redeem them or transfer them to another program. For instance, your 20K Starpoints are worth 25K AA, 25K CO, 55K QF, which equals 1 domestic round trip. Or, your 200K HHonors points are worth X numbers nights in a class X hotel. Etc...

The rules for each program get pretty complicated, so if you could simplify it and tell people what their options are, it would be valuable.

That being said, it would have to be pretty spectacular for me to pay anything for using it.

Good luck.