The TomTom Multi-Sport GPS Watch has a great record for being able to work with many smartphones and the Sony Xperia Z3+, Z4, and Z5 are no exception.
To connect your TomTom to the Xperia, you need to first go to Google Play to download and install the TomTom MySports App.
Before pressing Tap to Connect, you need to make sure you go to the TomTom watch's Settings->Phone->Pair New. The TomTom watch will then become visible to the App. After you select the TomTom watch, you need to enter the PIN that you see on the watch. If there is any tracking data stored on the watch, it will get automatically downloaded to the App and then uploaded to TomTom's cloud servers.
The Sony Xperia Z4's ability to withstand the elements make it an idea companion for the TomTom Multi-Sport Watch which can withstand the rain and even be used to track your movements while swimming. Thankfully both companies have put a lot of effort making sure their products excel in working with others.