Detecting loss of heartbeat

[Milhouse]

Hi, I have an Arduino device that sends a HTTP GET message to Stringify every one minute, as a heartbeat. I am trying to write a flow that detects a loss of this heartbeat (ie message not recieved for, say, 90 seconds) and then raise an alert. Can anyone advise how to do this?
I initially thought of using a Timer thing with a 60 second delay, like in the far bottom right corner of the example flows, but I don't think it would work as two consecutive messages would need to happen exactly 60 second apart, which is unlikely.
I also thought I could use Functions:Variables and have a variable which stored the time the last message arrived, or a timestamp. But I couldn't get this to work.
Any suggestions appreciated.

[Gary51]

That's a scary title- I thought you were trying to tell if someone died!

From your last post, it looked like Stringify needs to have https only, not http. Did you find a way to get the Ardiuno to send https? I don't have one, but after reading your last post, I got curious and searched around on the internet about that, and it looked like https on an Arduino would be pretty complicated.

Regarding this flow, it would be similar to the flows used to turn a light off if a motion sensor doesn't see any motion for a certain time. Like the flows in this post:

Porch Lights Flow With Timer Help [SOLVED]

If you don't get the heartbeat trigger, you would send an alert instead of turning off a light.

But if you try running any flow once a minute, or maybe even once every two minutes, and it goes all day, it will run into Stringify's limits and they will stop your flow.

[Milhouse]

Thanks again Gary! Will give this a shot.
Perhaps should also rename the post
I emailed Stringify and they confirmed they only support https. So I gave up on that, sent the GET message to IFTTT instead (as http), and got it to send a trigger to Stringify. Now implementing your proposed flows. Will let you know how I go.