It is probably done using some smart contract. In other words, your coins are inaccessible (can not be used/transferred) given a certain requirement. (For example after a particular date.)
I haven't researched how to do it though. It would be nice if their is a wallet where the feature is ready built in with user friendly interface and clear easy to follow instructions.
Iam not aware of any wallet offering this. I agree that smart contracts can offer this but I haven't used them.
I prefer to have control over my coins in case I really need to sell (need to pay for medical treatment etc) but not make it so straightforward that I sell on every piece of news. My coins are stored on a Trezor that is locked away. I have a watch only wallet on my computer so I can keep track of them.
Me too ;-).