Hi,
I have been using a watchdog timer in my project (card Requests - API Reference - Blues Developers) and it is a simple card.attn request:
J *req = notecard.newRequest("card.attn");
JAddStringToObject(req, "mode", "watchdog");
JAddNumberToObject(req, "seconds", sensorInterval * 5);
notecard.sendRequest(req);
I also know there are reserved environment variables you can use to restart the host every specified number of hours: Understanding Environment Variables - Blues Developers
You do need to connect the Notecard’s attn pin to the Swan’s EN pin for these to work, though.
I hope this helps!