The Iphone markup function works quite well, depending on the style of photos you're taking. I had a steel job with 50+ locations w/ nonconformances, scattered throughout 10 stories of steel skeleton. I would make my measurements then take a photo, scrawl the piece-mark/location on the photo away from the content, and move on. It was probably the most practical method because some of the locations were over 40+' from the floor below, and when the guy holding your ladder on the steel decking is 60+ years old, you want to be brief.
I would have preferred to use a more professional setup, but accessibility and line-of-sight can be very limiting sometimes. It will be even more interesting once the cellphone companies make dramatic improvements on their photogrammetry, or even LiDAR.