So since the v1.13.0 update I've noticed my Wahoo BlueHR heart rate monitor has had difficulty pairing with new apps while my Pebble was also connected. It seems that if I turn off my Pebble I can connect the heart rate monitor to the app.
If I've already had the HR monitor paired with the app then it seems like my Pebble can be turned on while trying to connect the app and HR monitor.
I'm not sure if it's the nature of low energy Bluetooth, but I haven't had problems using my car stereo via Bluetooth or syncing my Fitbit via Bluetooth while using my Pebble.
Anybody else have troubles?