HomeKit-certified devices are the slickest way to control your technology, but if you have any dumb technology powered by AA batteries, you can now remotely switch it on and off using your iPhone.

The Tethercell AA Smart Battery Adapter is a really simple idea. Replace one of the device’s AA batteries with this adapter, which takes a smaller AAA battery, and you can then switch it on and off from an app on your iPhone.

It’s Bluetooth LE rather than Wi-Fi, so range will be limited (the company claims 50-60 feet), but if the device is close enough, it’s a cheap and easy way to add remote control functionality. It’s compatible with all iPhones from the 4S onward.

The adapter costs $20 for two from Amazon.