For battery-operated devices, there is no real way to look at the cells and know exactly how much charge is remaining. Tethercell will not only give you battery life information, but also let you control the device using your smartphone.
Tethercell is a double-A sized enclosure that holds a triple-A battery replacing one double-A battery from your device giving you a smart battery. Once you have a Tethercell installed, you can use your smartphone to turn the device on or off, schedule device power, find the device or just to check the life of the battery. Tethercell only knows the charge status of the triple-A battery and since triple-A batteries have about half the life of a double-A battery when draining in the same device, you will need to replace the triple-A more often.
Tethercell works well with rechargeable batteries and you do not even need to remove the triple-A from the Tethercell to recharge the battery. It uses Bluetooth Low Energy communications, which will allow users to detect and locate any device within sixty feet. If you are tired of losing the remote, wondering if you turned off the baby monitor or if the smoke alarm is going to start beeping at three AM, check out Tethercell.