Does anyone have or know of any good, relatively simple, sonar type rules?
It depends on whether it was as an auspex or a sense.
As a sense, I'd probably say generally treat it as sight, but with 360 awareness, can only perceive vague shapes (and definitely no colour!), increased distance penalties and any penalties to hearing would also apply. However, you could also boost the character's hearing, I think.
Possibly, depending on the character, also some chance of getting confused each turn.
As an auspex, I might just treat it as a variant of a motion detector - many motion detectors are sonic, reading doppler shifts from anything moving.
That said, I think the default motion detector rules are highly messy, so there is lots of opportunities to do something clever.