At first the most convenient form-factor is a watch. It is always with you on your hand and it takes you the least time to look at it. Secondly the device must be waterproof, light and have a good battery life. Searching the Internet I found one igg.me/at/safeband/x . This smart bracelet has an opportunity to become a new standard of wearable electronics. Safeband works as an activity tracker, password manager (if you are distanced from your phone or laptop, it is closed on password, but if you are near it, you do not even need to enter anything) and tracker of your belongings: with the help of MiniTags it will announce you, if you came too far from valuables attached with MiniTag.