This is reputation linked virtual currency. Simple rules can be used to reward based on various user meta meeting certain conditions. This is only the beginning so bare with.
This plugin anticipates all the reputation based addons, like badges that will come out, and is implemented in the most flexible way, so that it doesn't have to rely on hooks being there, instead it create virtual event by listening to user meta.
It will also be able to be extended. Have a look at
KarmaBankMetaMap event in the MetaMap method for hints. CheckKarma is where the magic happens.
Simple payment API coming shortly.
Please sponsor any features you would like.
grep is your friend.