
Here is an app note from Linear Technology on how to use their LTMM2881 isolated RS485 transceiver as a isolated 5v power supply.
The LTM®2881 is an isolated RS485 transceiver that guards against large ground-to-ground differentials. An onboard DC/DC converter provides isolated 5V power to the output.

That is pretty cool, providing 1W across 2.5kV voltage differences, and allowing 20Mbps(!) at the same time. But $12 for the convenience of a floating supply?
Did anyone used the parts and passed radiated emission requirements EN 55024?