In reply to Pids:
I only know about Garmins, other brands are available
How fancy do you want it to be, and how much do you want to spend ?
All the new Garmins do stuff like step counting, smartwatch features ( emails, texts, FB notifications, etc on the watch ), bluetooth connectivity, etc. You'd pay anything from about £170 to over £500 depending on what features you want. Check out Vivoactive HR, 735XT, Forerunner 935, Fenix 5.
Note that I think the Vivoactive only works for swimming in a pool, but the others will work for open water swimming, which may be important if you do triathlons.
Older models that you could pick up second hand, eg 310XT, 910XT, 920XT won't have some or all of the above fancy stuff.
Also, some of the new watches are smart enough to wear as a day to day watch, whereas the older ones I mentioned above are not designed to really be worn all day, just for exercise ( ie the minute you switch them on they go into GPS mode which starts draining the battery ).
if after investigation you're interested in a 910XT, I've got one I've been meaning to put on eBay, would be looking for £80 delivered.