My house electrical system is divided into zones, each protected by a separate RCD. Occasionally one circuit trips, and sometimes it's a while before anyone notices. If it's the circuit supplying the freezer, for instance, that could cause a problem!
The home automation and broadband equipment is supplied from a UPS so I thought it would be useful to get a notification if a breaker tripped elsewhere in the house.
I bought a plug-in PSU enclosure and used a miniature AC to DC converter, an in-line fuse, a 5v relay and a modified Z-Wave door sensor to provide Indigo with mains power status. I've attached the circuit and a pic of the finished product. All components are contained in the box. The circuit shows a 240v AC input but the converter I used accepts 90v-250v AC so with a different enclosure the circuit would be fine for the US too.
I can provide component details if anyone is interested.