Great question! The closest thing I've found to this app is simply adding reminders as events to Google Calendar and setting up email notifications for each one. I'd say nudges is better in these ways right now:

  - Phone call notifications have been quite powerful in practice. I miss push notifications all the time, but a phone call is harder to ignore.
  - More powerful scheduling: some filters aren't possible to create (like "last day of month") in the Google Calendar UI

I'm also planning to implement more integrations (webhook triggers, webhook notifications, slack/discord/telegram/whatsapp notifications), which should tip the scales somewhat more. I also want to integrate Google Calendar at some point, so you could create nudges for all your calendar entries automatically.