Android/Windows: Potential is a dashboard of battery levels on all your devices. You can view it anywhere, set alerts for levels, and even toggle settings to save battery.
The app currently works on Android and Windows, with iOS and Mac on the way. Sign in, name your device, and it shows up in Potential's dashboard. You can add two devices in the free version, or add unlimited gadgets by unlocking the Premium version for $1 through an in-app purchase. The premium version also removes ads
Each device's current battery status is displayed along with whether it's connected to a charger, and if its Wi-Fi and Bluetooth radios are on. You can switch these off remotely to save battery, but be warned: You can't turn them back on. The premium version of the app lets you set a battery level threshold; if any device drops below that, you'll get a notification.