An accessory maker shared a picture of something many people would love: a clip-on iPad Pro keyboard with a trackpad. Sadly, Brydge’s concept device just isn’t possible because iOS doesn’t support external pointing devices.
At least, that’s true for now. But mouse/trackpad support is a often-requested feature, and there’s reason to think Apple is at least considering it.
UPDATE: Turns out Apple was considering it, and mouse/trackpad support is built into iPadOS 13. Learn how to use a mouse with your iPad.