I often wish I had some sort of portable light to use with my phone camera. For portraits, for dark places, for extra light, when digitizing paper photos, etc. Litra Torch and Lume Cube are the ones I have found that seems to be about right regarding both features, quality, and price. I haven't tried any of them though. I like that the Litra Torch has several LEDs, making it a bit wider. Both of them are magnetic, robust, chargeable by USB and about the same size.
Do you have a portable light or flash to use with your phone camera? Why did you choose it?
The video above shows a comparison test of Litra Torch and Lume Cube. The Litra Torch gets a few more points.