If you get a G3 hub (3rd generation), the bearings are sealed; older models may have free ball bearings with cups and cones -- you don't want those.

All PT hub models sense speed and cadence (though the cadence can be fooled, it's usually pretty good).

The current G3 models broadcast on both ANT+ and BT, so they're compatible with almost everything. This might not have been so for previous generation hubs -- you don't want those.

For the G3 models, you can get a campy freehub.

They're a mature product that generates reliable high quality data. Just keep to the current generation (G3).