In TSAPI in the private data version 17 features introduced in release 8.1.3, there are a set of capabilities that allow a TSAPI application to monitor for Service Observation activation/deactivation. These events include additional information related to the activity. Please reviewe the TSAPI documentation programmer's guide for more details.
https://www.devconnectprogram.com/fileMedia/download/b8929483-72e5-4dd0-907f-e99b112dad83
I do not know if this capability has been extended into JTAPI or DMCC.
With DMCC you could do first part monitoring of potential controlling stations and see if the lamp was activated, but that does not tell you who the observer was observing.
You could also use the DMCC Dashboard and create call control service monitor, and then observe the received XML to see if there are any events when the station, is observed, and/or when the station activates service observing. Using information in the even you could hopefully then back track into the documentation for that notification.