Raspberry pi pico personal diary or sorts

I was thinking, and this is something i thought about for a while, but i dont know if its even possible. its like a digital diary/notepad that you can write thoughts in without the need of a pen or paper. i have the idea and its pretty simple. its just a pocketable device, almost the size of a blackberry or even smaller. i want it to have a keyboard, but it can even be t9 to keep the small factor, a good enough screen and good battery life. but i dont know if its possible due to the pico being an mcu and what the ui will look like and how i will get it to be built. i have my own screen, raspberry pi, but im missing the keyboard and a battery that will be suitable.