I thought I'd update this thread as I've just acquired a Gossen Sixtomat Digital light meter. It's in good condition and seems to work well. Importantly for me, it's easy to use and to read (without reading glasses).
Unfortunately I didn't get good results with the light meter app on my iPhone so decided to buy this light meter.
Excellent choice! In the USA, these were called the Luna Pro Digital. And you are right, you can see the display without reading glasses. As for the smartphone apps, the ones I tried in Android were hopeless. You made the right choice, an instrument specifically made for the purpose you needed.
As for the smartphone apps, the ones I tried in Android were hopeless. You made the right choice, an instrument specifically made for the purpose you needed.
When it comes to Android it really depends on the quality of the phone. I use the Lightmeter app on my Honor9 (that's a 2017 model so dated by phone standards) and in daylight I don't bother carrying my Sekonic L508 any more. Once the light drops though the apps are limited by how low the camera can meter, which is generally 3EV and even that is not accurate. In any case, a dedicated meter is going to give you a lot more options so it is good to have one!