It is hard to recover a lost phone or tablet; and the consequences of a missing mobile device are substantial： So much information is stored in our mobile devices that we are at immediate risk of losing money， being burglarized， or even having our identities stolen. Think about it. Apart from having to re-create e-mail messages， change passwords and log-in names， recover pictures and secure financial accounts， online retailers like Amazon， eBay， and other click-and-buy services all assume it is you at the other end —even if it’s not.

　　Our feeble attempts to create and remember passwords are all but nullified if we use the “remember me” or the “keep me logged-in” tab on our devices， and how many of us carry a hard copy of our logins and passwords？ Cloud-based services are at risk for hackers as well， so putting your trust in a cloud-based data storage or password recovery system can be risky， as we have seen with celebrity accounts being hacked all the time.

　　It was not such a problem when fixed-location computers were desktop and tower boxes， but now our computing devices are small and transportable， so they can be lost or stolen more easily. Wearable computers in particular must “know” who is wearing them to be safe and useful.

　　This article looks at how biometrics can be combined with wearable technologies to help ensure that the person using the wearable computer is the one who is authorized to do so. This article examines some technologies that can verify a user’s identity and protect sensitive data， information， and control. All devices， datasheets， tutorials， and development systems referenced here can be found online on Digi-Key’s website.

　　Issues and concerns

　　Size is a problem when considering the use of biometrics in small， wearable computers. If your computer is the size of a postage stamp or smaller （and with wearable watch computers it is）， how do you justify the size， weight， and power burden of a biometric reader that is larger than your wearable device？

　　Placement is key as well. If a verification device is physically wired to the wearable computer in a permanent way， it is more secure than a plug-in or wirelessly linked connection. For example， fingerprint detectors and even retinal scanners can be a couple of square inches in area. These easily fit onto a laptop， tablet， or even a smartphone but are too large and bulky to fit into a stamp-sized device. The same may be true with facial recognition systems.

　　If plug-in or wireless connection of a user verification system is to be employed， it is best to do so as a “tethered” peripheral. Here the independent-verification system can do the detection， processing， and verification without any intervention from a host. This allows the host to query the verification system