Phone Improvements first appeared in the release notes for 2019.40.50 (official thread and discussion thread).
You can now read and respond to text messages using your right scroll wheel button. When a new message is received press the right scroll wheel button to have your text message read out loud and press again to respond by speaking out loud. You will also be able to view messages as they come in via the "Cards" section of the touchscreen.
To view messages that have been received while your phone is connected via Bluetooth, tap the Application Laucher > Call > Messages. You can read and reply to a message by tapping an entry in the Messages list. To enable this feature, tap the Bluetooth icon on the top of the display, and enable "Sync Messages". Once enabled you can also choose to play a chime whenever a new text message is received by enabling "Chime on New Message".
Additionally, if you have favorite phone contacts on your device, you can now easily access them from the Favorites tab of the Phone app.
Note: Notifications need to be enabled on your device from the phone's Bluetooth settings to send and receive text messages. Due to the limitations of Bluetooth support from your device, you will not be able to send group messages. As usual, Bluetooth behavior may depend on make and model of your device.