Signal isolation only I'm afraid. They do produce a tiny electrical output but it is measured in microwatts only.
Capacitive power isolation is possible but not recommended in most applications because there is usually no physical barrier between sides and also because the risk of the dielectric material breaking down is unacceptable.
If you look at photovoltaic MOSFET gate drivers like Vishay VOM1271 or fiber optic power converters like Broadcom AFBR-POC series, they are transmitting some electrical power through an optical link.
Inductive isolation is the most popular method to transmit power along with a signal, see e.g. Analog Devices isoPower device family.