Mean average precision (mAP) is a standard multi-class extension of average precision using OVR: https://en.wikipedia.org/wiki/Evaluation_measures_(information_retrieval)#Mean_average_precision

Recently I prefer AP over AUC so I think it would be cool to add this.
Maybe @gbolmier is interested? @thomasjpfan probably knows how to do this ;)