Apps for these two activities will be quite popular in my opinion. Using indoor running app Vivoactive logged only 16o cals for 1:30 mins table tennis where as Fitbit Surge logged in for similar time about 350 cals. Similar discrepancies with tennis between Surge and Vivoactive.
I agree with you it would be very popular. The Table Tennis club I play at has over 2000 members with a lot of interest in this app. I wrote Garmin many years ago why they don't have or develop a table tennis app. They have so many apps for sports less popular than table tennis; they have an overlap of similar apps yet they don't have this. Come on Garmin do we need to other hardware that have table tennis app???
Tennis would be on my wish list too. There is like SUPing and that sort, but tennis would definitely be very popular.
Since there is an acceleration sensor on the watch (Fenix 5 Plus), it should also feature some swing speed data.
I wonder, if the running adds, like running sensor would get the covered distance on a game of tennis running around the court. That would be most interesting to see. Golf app does count strokes automatically, from what I've read, tennis could be the same, taken you wear the device on your playing hand.