This website allows you to keep keep track of all your mileage accounts from one central location and know how many you have and when they expire. (meinemeilen.com)
I hope they do it soon because I keep losing track of what I want to read next! (kindleville.blogspot.ru)
We can think of the blockchain as a public ledger which keeps track of how many Bitcoins every address has. (bitfalls.com)