Not sure I understand the question. If you attempt to send a message, the screen from which you send it shows an “icon” (for each message) which indicates the status. Details vary by device. Most devices also sound a tone of some sort when the send succeeds.
The status bar at the top of the “home” screen does have an icon which indicates Iridium modem activity. This will be present (not continuously, but almost) while the device is trying to send a message. Also while trying to send a track point, or while doing an active mail check. This is a bit ambiguous. And it’s the “opposite” of what you want.
What I am looking for is a way to be sure that my message has been sent to the satellite. I know that there is a sound but sometimes I didn't hear it and I don't know how to be sure that my message has been correctly sent to the satellite.
Apparently Garmin has "improved" the UI on the M2 to the point where you can no longer see sent (or received) messages. Or maybe it was never there and I no longer remember that part. In any case, I do not see the screens now. So there is no way to tell that a message even EXISTED, let alone whether or not it was sent.
However, you can tell about the message you are currently trying to send. Once you click OK to send the message, you end up on a screen which shows the recipient, a portion of the message text, and the time the message was composed (I assume). There is an icon next to the message which indicates status of the send. As long as it shows the curve up-arrow, the message has not been sent. Once it has been sent, it changes to something else. (Not sure what. I am testing this in my basement office.)
If you leave this screen, the Messages glances shows Sending. If you press OK while on the Messages glance, you get back to the same screen.
My guess would be that once it is sent, you won't be able to find it at all anymore.
