Best list of arduino project ideas along with sources we have published here. It includes arduino based battery charger, arduino based thermostat and etc.
In this tutorial we will show how to build WiFi internet connected switch connected to EasyIoT Cloud. We will use solid state relay and Arduino IDE.
Ambilight system for every input connected to your TV.
Control over the internet (from anywhere) interesting as it uses a different port number
Use the WiFi module to make a web client or a server for your IoT projects. Or just use WiFI for inter-device communication.
One of the main problem in battery powered projects is to choose/use the proper battery size/model/type. As market is flooded now with a lot of low quality.