This can mean many things, here is what I have in mind:
If I use an Eliptical trainer, I want to log all the settings before I start. Similarly afterwards, I might want to capture several parameters. Sometimes it could be nice with photos (of the display).
I need timestamps for start/finish.
Next time I do come to same machine, I would like to see what I have done there previously.
In practice, I guess we are talking mobile app + web site - There seems to be fitness apps around, but they seem to concentrate on other areas. (I use Android).
NO PAID SOLUTIONS PLEASE!