Getting ADB to recognize the Motorola ET1 took longer than I'd like so I'm posting this with the hope that it'll help others who find themselves in a similar spot.
Like most Android-based devices, developers need to enable USB debugging on the device by toggling a setting in the developer section of the settings app. However, with the ET1, developers also need to add the device's vendor id (0x05E0) to the ~/.android/adb_usb.ini file or else the device won't be detected or visible to ADB.
Once the vendor id has been added, kill and restart the ADB server. After ADB starts back up, the ET1 should now be listed in the ADB device list and able to be deployed to.