The nice thing about Pocket Light Meter is the way the three "rolling scroll wheels" at the bottom function; simply slide the time or f/stop or ISO up or down, and the other readouts move as needed. In my sample picture, the ISO is set to 80, and the shutter speed was 1/10, at the f/stop of f/3.5. If I nudged the speed up, the aperture value would go wider, in perfect lock-step with the changing shutter speed.
For beginners, this shows the so-0called Exposure Triangle in a very graphical manner.
Another nice thing about this meter is the red "aiming box"; conventional reflected light meters, like the above-mentioned Sekonic and Weston meters, have a vague, generalized "just point it that way" angle of acceptance that is quite broad, and utterly un-defined by any kind of aiming device. With the Pocket Light Meter app, you KNOW, exactly, where the metering is being done. It might seem like a gimmick...but it is actually the best reflected light meter I have ever owned, and I have owned four different ones over the past 35 years.
Now, if they made one that could meter FLASH pops...