Yes, I think you are right. Using the headphone jack would probably be a much much better idea.
My concerns are with the addition of the bluetooth (BT for short) which conflicts with wifi (particularly since the RW phones use the 2.4 GHz wifi band - same as BT). I was using a PhoneLynx which gave me erratic performance, I've blamed that on BT WIFI conflicts but who knows?
I just received an OBI 202 and an OBIBT card and have been testing this out tonight. So far so good; but it seems that a straight google voice connection from the OBI is better quality than the added BT to the RW phone (at least on my very limited initial impression so far). This would lead me to just use GV. But GV can't port my phone number (RW could - and did) and I want to use a single number for all outbound. GV doesn't seem to be able to do this. Ideally I want 1 number to be where it looks like I'm calling from whether I'm using GV or RW wifi or cell. Sounds kind of weird; but I'd be willing to hardwire the RW phone instead of using wifi as well. $5/mo can't be beat for a dedicated phone line that can use my existing number (which GV can't do).
Ring.To can port my number. I might consider the OBi with them next ... don't like their voicemail though ... and I'm actually liking the google hangouts integration with GV nowadays.
So far, the performance appears to be ok. Hard to tell w/o much more testing though.
BTW, anyone know what kind of performance hit I'd take if I ported my number to
Ring.To and forwarded all calls to multiple phones (GV, RW)?