Thanks very much for the info!
I tried something different today - I deleted the app from the phone, paired the phone to the bike, reinstalled the app and then ran it. The 'Connection Lost' prompt immediately appeared again, despite the bike being shown as connected in both the iPhone Bluetooth screen and FX dash display (the phone was within 5 feet of the bike at all times). I've never seen the bike's ID appear in the app, only in the iPhone Bluetooth screen. I think the Android app handles the Bluetooth pairing, while the iPhone app has the phone do it. I'm about 90% sure the problem is in the app and not the phone, although it might be in the bike for all I know.
I don't have access to an Android and rented an iPhone 5 just to use with the app, so I can't really swap out the phone.
I spoke to Nicholas at Zero tech support today, who's been helpful in the past. He told me he'd look into the problem and get back to me, including the strange Bluetooth ID my bike has.
Ray