I recently asked another question, but I deleted that one because I can narrow down my question to something simpler.

Suppose an ethereum ERC-20 token contract can emit the following event:

event Approval(address indexed owner, address indexed spender, uint256 value);

Is there a service (paid or free) I can use to watch for this event and be notified preferably by SMS (or email) whenever it is emitted?

2 Answers 2


You can use OpenZeppelin Defender it has a Sentinels functionality that allows to monitor a deployed contract, and you can choose to be notified via Email, Slack, Telegram, or Discord, push data to Datadog, or execute an Autotask in response to a notification.

*Note: I'm not affiliated with the products mentioned.

  • 1
    Thanks for the suggestion! Hadn't heard about this. I'm willing to pay for the service but from their pricing table they have no individual plan with mainnet access. I would need the "Teams" plan which is $500/month. Too rich for my blood. Have you heard of tenderly.co? They are built with monitoring/alerts in mind, have a 14 day trial and $80/month gets it done. Am not affiliated, but trying it just now. Only downside might be no SMS notification Oct 31, 2021 at 1:36

I decided to use the Tenderly.co service. It does not offer SMS notifications, but there are other options that will have to do for now, such as email.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.