There are so many electronic devices to charge, your cellphones, headsets, watches, gaming controllers, tablets, laptops, etc. Create a base station that could provide power to each of these devices using technology that Nikolay Tesla invented in 1897. A single basestation that you place in the center of your house that can charge all these devices in your home.
If the device could be produced under a price point of $100.00 then the markup would be 50%. Additional longer range or higher wattage devices could generate more revenue as they could be sold at a premium to the standard version.