Brightershade – welcome to the forum.
I don't have an OBi202 and the AdminGuide is well out of date regarding Blue Tooth issues, so here's my semi-educated guess:
Incoming calls to each service on the OBi202 need "bt" added as a terminal. For instance, if Google Voice is on sp1 then your exisiting sp1 InboundCallRoute probably looks like this:
Voice Services > SP1 Service > X_InboundCallRoute:
{ph,ph2}
Change it to:
Voice Services > SP1 Service > X_InboundCallRoute:
{ph,ph2,bt}
Now incoming calls on sp1 should call phones 1&2 and the Blue Tooth paired cell phone.
As I understand it "bt" = Blue Tooth Service 1 and "bt2" = Blue Tooth Service 2.
Edit: Having looked at this again, I'm not sure that this will cause the cell phone to ring. More likely it will simply connect to the cell phone, which will expect to receive digits.
Make the changes via the OBi Expert Configuration pages. From your OBi Dashboard, click on your OBi number and follow the prompts to get there. To change a value uncheck both boxes to the right of the value and leave them unchecked. After changing the values on one page, press submit at the bottom of the page and wait a few minutes for the OBi to reboot.
For outgoing you could use the OBiON app on your cell phone, which will work anywhere you can connect via wifi. The default setup allows you to use "single-stage dialling" using the OBi202's Primary Line. This can be improved if you want to go with this option. You could also use the OBiON app for incoming calls – it needs some changes to all the other InboundCallRoutes to achieve this and does add extra "legs" into the call route which may affect call quality.
If your cell phone is android, then there is a way of using CSipSimple to make your cell phone into a wifi handset and connect to the OBi via a wifi router. This is a little complex to set up, so I won't try that here unless asked for.
Good luck – let us know how you get on with {ph,ph2,bt} as I don't recall it being posted here before.