This app looks like a nice clockface. But behind its simple looks this app monitors the exchange rate of the Bitcoin and alerts you with a buzz on your wrist when the rate exceeds or drops below boundaries you have provided in the setting screen on your phone app.
Checking the Bitcoin rate is by default every 15 minutes.
You can set the app reflect the value of 1 Bitcoin in American Dollars, Euros or British Pounds.
The rate displayed and used in equations is obtained from coinbase.com and reflects the Spot Rate (which is usually in between the current sell and buy price).