You can extend FOP2 via plugins. There is one free plugin you can use for this purpose already, the "mini browser" plugin, together with enabling notifiy_on_connect=1 in fop2.cfg and configuring a popup in your user preferences or globally via checkdir.php. Here is an article talking about configuring FOP2 and popups:
http://members.asternic.biz/knowledge_base/fop2-popups-and-variables
So you can write some php code to either retrieve data when a call is connected, and present a form to update/add new data.
The Tag Queue Calls plugins does that, but instead of notes you can select "tags" for a call, and the data can be retrieved later with Asternic Call Center Stats PRO for reporting.
Best regards,
