Bluetooth and ANT+ sensors will communicate within a few feet of the bike, although it varies with sensors and transceivers. All my sensors will reliably communicate with my phones or bike computer regardless of where the sensors are mounted on the bike.

That's a big improvement over the older style wireless bike computers with magnet based sensors that needed to be mounted on the front wheel. I got one of these generic bike computers (no GPS, etc) a couple of years ago that works fine, but only with the speedometer/odometer sensor on the front wheel. The wireless signal wouldn't even reach the rear wheel. So it was useless when I was using the bike on an indoor trainer, unless I mounted the receiver on the top tube rather than on the stem or handlebar.

The Bluetooth/ANT+ computers will easily reach the rear wheel or anywhere else on the bike (not sure about a tandem, haven't tried).

When I was in a physical therapy clinic for a couple of months last year, 2-3 days a week, I'd wear my Wahoo Tickr heart rate monitor, but I left the phone running Wahoo Fitness in a chair in the waiting area. Often I was 20-30 feet away but the Tickr never lost connection with the phone.

The XOSS G+ computer wireless transceiver isn't quite that robust. It wants to be closer to the sensors and/or phone to make a connection. As distance increases between the G+ and sensors or phone, errors creep in or it'll take longer to transfer data after a ride. So I usually set the XOSS G+ and phone on a desk or sofa next to each other to ensure quicker data transfer. But I've had no problems with data logging during a ride.

So far in 5 weeks of using the XOSS G+, 2-5 times a week for just over 1,000 miles of rides, I've had only a single glitch when a ride log failed to transfer from the G+ to my phone for uploading to Strava. That's no worse than reports I've heard from friends who use Garmin and Wahoo computers. A week or so ago I reset the XOSS G+ and reinstalled the Android app to clear up a glitch. It now works fine again, although I lost some custom notes I'd entered for each ride. But the raw data was preserved accurately.

With any wireless computer there's usually some lag between what's actually happening on the bike and what shows on the computer display. That was true with my phones when I used them, and still true with the XOSS G+. I've noticed this with speed, cadence and gradient. I've heard that Bluetooth transmits a little faster than ANT+. However there doesn't appear to be any way to choose one wireless protocol over another with the G+. I'm assuming it defaults to ANT+ because this enables sharing sensors between two receivers (the G+ computer and my phone). I'm not sure whether Bluetooth supports sharing sensors with two or more receivers.