Nasa BM-1 Wireless Battery Monitor
The NASA BM1(BT) Bluetooth battery monitor hardware (sold separately) is supplied complete with a 100 Amp 50mV shunt and all necessary cables to connect to the main service battery. It is intended to monitor a 12 volt lead-acid battery, or bank of batteries, with a total capacity between 5 and 600 Ampere-hours (Ahr).
The information is transmitted using Low Energy Bluetooth (Bluetooth 4.x or higher) and can be viewed on any compatible device running Apple iOS 9.x and WatchOS 2.x.
Update for iOS 12
Minor cosmetic changes
Up to six family members will be able to use this app with Family Sharing enabled.