Purchased on Amazon as a gift from my Mother-in-Law, and had it since Christmas and all of a sudden the lens cracked...never hit it on anything or anything like that, a small crack appeared one morning then it grew steadily worse--looks to be on the verge of shattering, see pic.  I've owned many watches and never had a lens on the verge of shattering (scratched?  Yes. Cracked? No.)  Saw several articles on line about this, and one good one from C-Net about manufacturing process.  Buyer beware.  Also used this at Disney and 3 other people had Apple watches and Fitbits and registered consistently about 20,000 steps a day (including my own Samsung phone!) but the watch recorded 16,000 steps...maybe has to do with the cracked lens?
 Contacted Nokia and am getting the run around already, will adjust ratings if they come through, but apparently the serial number is on packaging and I'm sure the next email from them after pictures sent and repeated attempts will be "tough cookies", so so yourself a favor and save your box!  (or go Fitbit)

Update:  Withings sent me a postage paid envelope to return watch for repairs...looks promising, I'll keep you posted.  BTW- I found the serial number on the app.