Looking at these sorts of things is always a little bit mind boggling. This reminds me of the Tikker death watch that's on Kickstarter right now that counts down to your (statistically likely) death. I'm really curious what sort of effect wearing something like that would have on a person - constantly being reminded how long they (probably) have left to live. On one hand - I might go crazy and be overly cautious and think way too much about my safety to enjoy my life at all; on the other; maybe I would instead go out and enjoy my life to the fullest and go travel and do crazy things, etc. It's an interesting thing to wonder about.
My friend has one tattoo, it's a tiny exclamation point that is normally hidden under the face of his watch. It's to remind him that time is of the essence. I suppose if he'd of had the "Tikker" he wouldn't have needed the tattoo.
It's none of my business, but I'm of the mindset that you should go out and enjoy your life to the fullest regardless if you know when you're going to die or not. Your life is already yours to own. Use that thing. Make sure you don't stop living in order to stay alive (and that last piece was lyrical theft; credit belongs to The Offspring).