The OBiON app can be used from your mobile phones.
First set up your softphone number in your OBi Dashboard. Input your OBi110 number in the "Obi Voice Gateway" section. Then download the OBiON app to your mobile phones.
If your Google Voice service is your Primary Line, that is you don't need to use ** codes, then you should be able to dial 011+ from your OBiON app the same as from the house phone.
Two caveats:
1. OBiON app seems to only work reliably when connected via wifi (plenty of free wifi around these days). 4G should work well, but I'm still on 3G, so I cannot confirm that.
2. Only one OBiON app can be logged in at one time using the same account. Whoever logs in last will have the connection. There are ways around this, but no need for extra complications in this post!