Well, do do a .fit file in a watch-app, you do it by way of ActivityRecording.
If you want to save something between runs of your apps (only your app can access it) you use Application.Storage.
If you want to save something to a log file, you just use something like Sys.println() for console output, but you must pre-create the log file on the watch in \garmin\apps\logs named <myapp>.txt where <myapp> would match <myapp>.prg. And remember, when downloading from the store, <myapp> is generated by the store (an 8 char string) so you'll have to figure out what that is. Also, when the file get to a certain size (5k or so), it becomes a .bak, and a new .txt is used, so you can have about 10k at most. This really only should be used for debugging on the watch.
But I cannot create an arbitrary file on the watch and write something there, like .dat file for my own data or .JPG image of something or modify .fit file manually, etc.? It is correct?
Correct.. With CIQ, you can write to a fit file, but you can't even see that file's name. With Application Storage, those files are named based on the store generated name if installed from the store. And log files need to be precreated, which again is based on the store name, if the app store was involved.
