How can i use the Bluetooth HID Device profile in Android Pie?

Currently on pixel the HID device Profile is enabled . Nokia, moto(as mentioned above) and One Plus 5T and 6 as far as i know dont support this profile.

We have created an app which lets you use your phone as a bluetooth mouse and keyboard with this HID device profile. https://play.google.com/store/apps/details?id=com.github.roarappstudio.btkontroller

The code is open sourced at https://github.com/raghavk92/Kontroller. If anyone wants to help in making improvements or contribute to the code they are welcome.

You can also check if your phone supports Bluetooth HID device profile with the app - https://play.google.com/store/apps/details?id=com.rkaneapplabs.bluetooth_hid.bluetoothproxy and let your device manufacturer know if they dont support your device because its part of android pie and should be supported.

List of devices that have the Bluetooth HID device profile activated/Not Working(due to manufacturer implementation bugs) is here - https://github.com/raghavk92/Android_Bluetooth_HID_Device_Profile_CompatibilityList

The bugs are due to implementation on the manufacturer's side not google as pixel devices support this Bluetooth HID device profile since android pie

You can have a look at this https://github.com/kshoji/BLE-HID-Peripheral-for-Android . I was able to build a bluetooth keyboard out of this.

There is a semi-official sample code available here: https://github.com/ginkage/wearmouse — actually by Google itself (see https://opensource.google.com/projects/wearmouse).

It is intended for using on Wear OS watches, but has everything you need to use it on a phone as well: proxy class for the profile, a callback class, HID Descriptor example, QoS, callbacks for cases like battery level inquiry from the host, etc.

The app itself is available at Google Play here: https://play.google.com/store/apps/details?id=com.ginkage.wearmouse (the app supports Android 8 as well, by the way, but that only works on watches, not phones).