Wow... I wonder how much time does logging of all those tasks take time? I'm not sure if I could do it since I'm switching among tasks all of the time. Manual logging of activities does take some time but I guess it it more precise than application that comes with some fitness wristband.
He said it takes one minute total, per day, using his app. Previously 10 minutes.
Just to share my experience, the time spent recording data often feels like it's worth it; there's a tangible reward that's more obvious after a while. At first it had novelty value but years later I recognize it as a distinct value separate from novelty. The act of recording by itself has a noticeable impact and anchors a feeling of self-control. (I use a sloppy tag-and-gather method though, not an app, which seems like it could be really fun to create)
I use a text file where entries have a start timestamp, end timestamp, and a description. I have a macro to automatically enter the timestamps. It takes about 5 seconds to make an entry and about 4 minutes if I'm doing all the entries at once.