Please, i'd like to build a small application(using kotlin) that can be installed into a device that is movable. Would also like that i can maybe connect to the device via a console to configure certain things. The device should also be able to broadcast hotspot etc... Where can i start from or what can i read more about this.

start by learning kotlin, kotlin native, and the specific api for the device you wwant to create the application for..

i already write kotlin..

Buy a raspberry pi?

hmmm... currently don't know how that works, but i will read on it