Smart watches. How to choose?

There are so many wearable smart devices? Which properties should they have?

Should they have encryption functions, or track the activity?

Have you ever heard about Safebad? Is that a good device?

From what I know,  I can't afford one,  do you have any updates,  be nice to hear your thoughts if you do have one,  I know they are coming along with that technology but at the same time,  this technology has been there before except it cost a whole lot of $$$$,  military comes to mind as the testing field…if it works there then it should work anywhere.