You can use mdbus2 (in extras-devel IIRC) to listen to and inspect d-bus. Just make a call, let it ring, stop calling.
Also, there are call log apps around, download and examine them. It might be that there is a status flag in the call log database that could be useful to you.
Use gobject.timeout_add_seconds for a more efficient blinking. Don't use animated gifs, just use two icons alternating between them.
The yellow window might be related to the hildon notification. Or just compare the process list before and after having a missed call.