Your phone may not cause cancer, but it does emit enough electromagnetic energy to power a small device. Concepter’s Lune smartphone case detects when you’re receiving a call based on the wavelength of your cell signal and shows a green light to alert you, using your phone’s energy field as its only power source. We had a chance to test the Lune at CES 2014 and were amazed with its unique use of energy and radio waves.

The version of the Lune case we saw was made for an iPhone with a simple black design and a light ring around the Apple logo. However, Concepter told us that it will also make versions for other phones and that the final version will have different lights for call and SMS message alerts. [Battery Life Champs: Longest-Lasting Gear of 2013]

As we held the phone, a Concepter rep called its number and the green ring on the back of the case lit up. We were particularly impressed to see that the Lune was able to identify that the phone was receiving a call, not from a Bluetooth signal but from the wavelength of the phone’s GSM signal. Concepter told us that future versions of the case will be able to read CMDA signals so they can work on Sprint and Verizon networks. They will also be able to read the wavelength well enough to tell that you’re receiving an SMS message and light up accordingly.

Concepter will be putting the Lune on kickstarter in the next few weeks with an estimated price of aroound $35. We look forward to seeing what this innovative product becomes when in its final form.

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This story was originally written for LAPTOP and has been republished with permission here. Copyright 2013 LAPTOP, a TechMediaNetwork company.