Unda Ltd had a stand at the Our House Show in Punchestown.
At first glance it appears to be an electric boiler, but it's actually a
"Griggs Machine" or cavitation heater.
According to their website the thing has an C.O.P of 2.0 which is like a heat pump, but there's no heat source other than the pump.
Unfortunately the pump is three phase which rules out most rural one-off houses.