It is possible to determine whether a region is on an original host or the cloud by examining the host name of the simulation, but many users aren't familiar with the arcana of doing so. Fourmilab Cloud Halo is a light-hearted attachment which makes it easy to see the hosting status wherever you happen to visit and alert you to changes when you arrive in a new region.
The Cloud Halo comes with a user guide notecard, that allows for some
adjustments. Trying it out, it did the "wah-wah" sound and faded after
briefly appearing as metal. It took some time flying around, but
eventually it lit up and did the harp sounds. Besides the pictures I
took, one can also check out a Youtube.
John Walker (Fourmilab Resident) is the man behind the Cloud Halo. He has a number of other products on Marketplace, all of them free.
To get the Cloud Halo, Click Here: https://marketplace.secondlife.com/p/Fourmilab-Cloud-Halo/20555301
Hat Tip: Hamlet Au