I just checked for this (supposed) v1.4.0.1 firmware update, using both the Nexus 7 LTE, and Asus ZenPad S 8.0, but, before I get into what I found, something else of interest happened. Prior to updating the app on both tablets, from DJI Pilot v1.20 to DJI Go v 2.0.0, I updated the firmware on the P3P, transmitter, and all three batteries, from FW v1.2.6 to FW v1.3.20...and, yes, i double-checked the success of the updates, via the .txt file created upon completion/failure of the firmware updates, just to be sure. Just now, while checking the update availability of the firmware through the transmitter, it told me that the current version was (still) 1.2.6, to which it updated (again???) the firmware to version 1.3.20. After completion, I shut down the transmitter, as instructed, but, before starting it back up again, I went to the Google Play Store, only to discover DJI Go already has an update, from v2.0.0 to v2.0.1, which I'm currently updating on both tablets.
Moving forward...after updating the app on the ZenPad S, followed by restarting the transmitter, and checking a second time, it turns out that, as reported, there IS a transmitter-only firmware update, to (again, as previously mentioned) v1.4.0.1...as soon as the transmitter is updated with the newest firmware, I'll check to see if there are any new features/functions, and, if there are, I'll report back.