I've been using the G9 for a year or so...
Works reasonable as a bike to bike intercom, though it's flakey.. almost an art getting it to sync with other people... I've had 5 of us on once, but sometimes getting 3 is a chore.. It's something you get a feel for, and it gets easier.
But using the phone as a GPS, we always get kicked off intercom.. it's really buggy about this.
The +9 is not what you expect either...
If you are riding in a group you will likely be paired up in 2's or 3's... and if someone on your G9 list is on intercom A or B.. trying a G9 call to them will get you the response "busy"... I've not tried the "emergency signal" as a way to get everyone to back out of intercom. But it's pretty chancy getting the non Channel A or B to connect if people are chatting.
I use it to listen to music and Navigation when by myself.. it works great.. I use it to be involved with other riders when riding in groups and it's great.. But doing both is a stretch too far.
One thing we always chat about when riding together is the design of a better intercom... I'd love it of someone got an add-hock wifi network on android phones as the bike-to bike.. then bluetooth headset to the phone... It could maybe enable voice chat with quite a few at once... it could even be intelligent enough to align the phones to stretch out the network along the chain...
Al...