heated O2 sensor circuit question

[xxalexx at ix.netcom.com]

> I plan on relocating my O2 sensor further down into the header since the
> original spot reads off only 2 of the 4 cylinders. Thing is, the
> original sensor is a single wire, and I think I'd need a heated one for
> the new location. 
> Any idea how to wire the heater circuit? Is it safe to wire the circuit
> to a switched (engine on) power source or was the heaer designed to shut
> off once it reaches operating temp?
> 
wire to key on with fuse, keep wires away from driveshaft.
alex