I use a smartphone app (iOS and Android; iOS in my case) called Cyclemeter to log my rides. It has a feature that lets you automatically send position updates to registered contacts every N miles or N minutes, which I used to update my wife when I was riding the Southern Tier. Obviously this is dependent on decent cellular coverage, which can't always be taken for granted. iPhones also have a "find my friends" app that you could turn on. I don't know how much this chews through the battery compared to other options; I assume Android has something similar.

There are some high-end bike computers that will interface with your phone, and some smartphone apps (the aptly named Bike Computer is one) that also have crash detection, and will send a notification if they detect what seems like a crash, based on accelerometer data.

The Spot trackers are the only kind of device I know of that aren't dependent on cellular coverage.