RCS (Rich Communication Service) was meant to elevate regular SMS to a competitor to iMessage, but the rollout by carriers had been slow and support patchy, until Google took matters into their own hands and brought RCS support directly to the Android Messages app.
Compared to iMessage the range of features supported is small, however, but it appears Google is testing one upgrade in the wild.
The feature has been in development for some time, as teardowns of the app have shown but it now finally appears to be rolling out to some consumers.
If a recipient does not have the feature in their RCS client they get the following message:
The feature does not appear to have rolled out very widely yet, but we assume after a bit of testing it won’t be long.