Parents can now help their children study - by buying a ball and chain that only unlocks when they have studied for long enough.
Concerned moms and dads set the desired study time on the Study Ball and attach it to their child's ankle.
A red digital display counts down the 'Study Time Left' and the device beeps and unlocks when the time expires.
The prison-style device weighs 9.5 kg (21 pounds), making it difficult to move while wearing it.
It cannot be locked for more than four hours and comes with a safety key that allows the manacle to be opened at anytime.
The ball and chain costs £75 and is sold online at curiosite.com.
The website says: "Quite often, students who are having problems concentrating tend to get up every ten minutes to watch TV, talk on the phone, take something out of the fridge, and a long list of other distractions.
"Were they to dedicate all this wasted time to studying, they would optimize their performance and have more free time available."
Designer Emilio Alarcon said: "The project was born of a conversation I had with a friend who was studying for a civil service exam. He said: "I haven't left the house in a week, this is like being in jail"."