The tool monitors SMS message additions and SMS state updates, e.g.:
$ sudo ./test/mmsmsmonitor
[/org/freedesktop/ModemManager1/SMS/0] sms found: received
[/org/freedesktop/ModemManager1/SMS/1] sms found: received
[/org/freedesktop/ModemManager1/SMS/2] sms found: received
[/org/freedesktop/ModemManager1/SMS/3] sms found: received
[/org/freedesktop/ModemManager1/SMS/4] sms found: received
[/org/freedesktop/ModemManager1/SMS/5] sms found: received
[/org/freedesktop/ModemManager1/SMS/6] sms found: received
[/org/freedesktop/ModemManager1/SMS/7] new sms: receiving
[/org/freedesktop/ModemManager1/SMS/7] sms updated: received
