*client* reference implementation of subscriptions on Ethereum
https://tokensubscription.com allows publishers (service providers) to deploy a smart contract on Ethereum with parameters for a subscription including destination address, token address, token amount, and period of recurrence. The publisher then supplies a link to the subscriber that is presented with the terms of the subscription to sign an off-chain meta transaction that is replayed on the defined period. The subscriber controls the flow of the tokens (starting, stopping, pausing, etc) using the ERC20 standard approve() function.
Usually a nonce is used for replay protection, but the heart of the trick with https://tokensubscription.com is a replay-able nonce that works on a defined schedule. In combination with the ERC20 allowances and meta transactions an extremely simple token subscription service can be created.
https://devpost.com/software/token-subscription
