As of R2.7.0, it is possible to send and receive short status messages on radios and dispatchers. The status message is only a few bytes and is sent across the control channel which frees up the system (since text messages are sent over a traffic channel). This appears to be very similar to SDM1 in MPT1327.
Rather than sending an entire 288 character message (plus call setup), the radio merely sends a number that has a meaning on the destination radio/dispatcher. Examples include "At the Airport"; "At the Hotel" or "Arrived on Scene" - each of these would be allocated a ststus number.
This feature is only available in Capacity Max. Up to 100 status messages can be configured in radios and consoles.