This was just posted on the status page.
North American Device Health Outage
Resolved - Users should now be seeing device reporting the correct health status. We have identified and resolved the issue. Thank you for your patience.
Jan 9, 10:34 EST
Well, that may be but I’m not turning it back on at this point. I am not sure what the upside is.
If its working properly, the upside is it brings your attention to devices that have fallen offline.
Good point! don’t need to do flailing in front of your motion sensors 
I agree that having that information would be nice. However, “If its working” is the issue so far, Not only does it not properly report disconnected devices, it actually seems to be pushing some of them off the network instead. So, there seems to be no upside and all downside currently.
Seems to be user specific. Works great for me.
I’m sure you’re correct. However, from what I read on this site, it (anecdotally perhaps) seems to me that there aren’t very many on the’ “it’s working great for me” side.
Hopefully, that’ll change soon.
Yup. That’s what I use.
@Danabw, thank you! I didn’t know about this app and will install ASAP. Take care.
Shoot, I am doing something wrong and can’t see the app in my ST Mobile App.
- I copied the code from your link, hit publish TO ME
- Hit App Setting, went to OAUTH (I dont really understand what this does but Ive done it before), then hit Update.
- Then in my ST App, went to Marketplace, MY APPs, and presto, it wasn’t there.
I looked at MY APPS in the IDE and it appears to be there. I am probably missing a step. Can someone help please?
My Iris product (motion and contact sensors, smart plugs} have been the most reliable devices I have until recently that is. Over the last 3 weeks every motion sensor has dropped off the system. Yesterday was the 3rd time but only one went out. The ST heath checker is another wasted effort from ST. What’s it been now, a year that the health checker has been in place and it still is worthless. lol
Go to Automation>SmartApps, scroll to the bottom and select “+ Add a Smart app.”
Then scroll to the bottom again, and select My Apps.
looks like you’re on the wrong server. Your IDE screen shot doesn’t have the MyQ or Core Smart app that your phone has. Make sure you’re using https://account.smartthings.com when you login to the IDE.
Beat me to it, Jimmy. That could be it, a wrong shard issue. If the IDE SmartApps list and the My Apps list in the app aren’t the same, that could be the cause.
Thanks everyone - it worked great! Now to play with the app. I appreciate everyone’s help.
Everyone may already do this but I had an idea. It was a little hard for my old eyes to see details of this Simple Device Viewer so I copied the URL from my mobile device and emailed it to myself. Sure enough, I am able to view it in the browser. 
Here’s a little more for everyone on logging in through the official url https://account.smartthings.com.
Not to add more complexity to the number of people who end up logging into the incorrect shard because of previous posts in the community or from links posted in official ST Docs, but I wanted to share this with everybody and make sure to pass this on.
There are actually two scenarios when logging in through the official url above:
- After successfully logging in, a person is redirected to their correct shard:
- https – graph-na02-useast1.api.smartthings-com
- https – graph-na04-useast2.api.smartthings-com
- https – graph-eu01-euwest1.api.smartthings-com
- This does not include all valid shards – However if they are redirected to https – graph.api.smartthings-com, goto 2 below.
I edited the urls so they aren’t clickable
If you are redirected to any of the above urls, a person can then proceed as normal.
- After successfully logging in, if a person is redirected to the following shard https – graph.api.smartthings-com then:
- That person needs to goto Locations
- Select their Location (some people have more than one)
When they select their Location they will either be:
- Redirected to their correct shard listed in 1 above -or-
- They will remain on https – graph.api.smartthings-com which ultimately is the correct shard.
Number 1 is the more common scenario to happen especially with newer people in the community, but there are people who either get directed to graph.api… first and then redirected after selecting location and there are people who (usually members who have been with ST for a long time) do belong to graph.api.smarthings… <— confirmed by a ST staff member and also by me in working with a UK member the other day with another SmartApp
At some point I will get this into some sort of community documentation. Who knows, with all the news around merging of applications (ST and Connect) maybe the urls will all change again.
Including @JDRoberts as one of the community specialists.