Smart contracts in plain JavaScript.

// A subscription that fires itself.
// Customer signs once. Cron does the rest.

function subscribe(amountPerWeek) {
  storage.set('sub:' + msg.sender, {
    amount:     amountPerWeek,
    nextCharge: chain.timestamp + 7 * 86400,
  });
  cron.schedule(this.address, 'chargeAll', '@daily');
  emit('Subscribed', { user: msg.sender, amount: amountPerWeek });
}

// Auto-called every day by the chain itself.
function chargeAll() {
  for (const [addr, sub] of storage.entries('sub:')) {
    if (chain.timestamp >= sub.nextCharge) {
      E(ASE).transferFrom(addr, storage.merchant, sub.amount);
      sub.nextCharge += 7 * 86400;
    }
  }
}

Deployed as plain source. Readable on-chain. Verifiable in a single hash compare. Reentrancy structurally impossible.