Is doing this possible through smart contracts?

I've been trying to lose weight over the past few months and so far the progress has been great - however I set a target for myself that if I reach X kg i would reward myself by buying a new phone - but I'm very tempted to sell my ETH to buy the phone, and I've been learning solidity for a few days, so I am interested to know if it's possible for me to:

1. Lockup my money in a smart contract
2. Create a way for the blockchain to be able to receive my weight data from my health app (maybe through an oracle or something?)
3. Allow the smart contract to release my funds provided I have reached my weight target

Any ideas? Would love to be able to do this, and it would be a nice starter project for me to try and make with my future solidity experience.