German mechatronics engineer Johannes Heberlein has launched a new photo accessory on Kickstarter, the Lime One compact hot shoe light meter. The meter has been designed to be very easy to use, and even updates its readings in real-time.

In 2018, Heberlein started using film cameras, and he immediately found his light meter options somewhat lacking. He started using a smartphone-based solution but became frustrated with needing to constantly take his phone out of his pocket, get an exposure value and then put his phone away. 
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https://www.dpreview.com/news/5079235474/lime-one-is-a-compact-easy-to-use-light-meter-you-attach-to-your-camera-s-shoe-mount