I think at the very least one needs a reasonably accurate pedometer, preferably one that can interface with the phone. I can use one that also provides distance and average pace, since I do both walking and runing intervals. These types of statistics and more are now provided by Strava. Since I have been really pushing myself at my age, an accurate heart rate comes in handy. I really need to not go much over 160. Besides, exercising by zones can be helpful. Anything beyond that I do not really need to use. Perhaps a good fitness watch is all that I needed due to my heart rate concerns.

Assessing calories by the watch is not necessary and is fraught with variables that can effect accuracy, which was the primary reason I went to a sports watch. I am not so sure now. I am beginning to think that sport watches are necessary only for accurately evaluating performance, which I do not need. Leave these things to the competitive runner.