If you are in the market for a very cheap computing device to install your own operating system, and need a screen, keyboard, touch pad and a battery pack, don’t buy a Raspberry Pi. Instead buy Chromebooks which are at End of Life (EOL) and are selling very cheap.
This Asus 11.6″ Chromebook C202SA reached its EOL this last month and distributors are trying to get rid of the remaining stock. This specific unit is available for just $37 which is way less than what you would get with Raspberry Pi or other alternatives.
Chromebooks generally have a lifespan of 5 to 7 years after which they stop getting OS updates from Google. While the device continues to be usable, they may not get critical updates to protect you.
However, most of these devices can be modified to run other operating systems and would perform far better than solutions based on Raspberry Pi.
There are a few different ways to run Linux on Chromebooks. The one I recommend involves some creative hardware hacking which is documented here. Note that this will void your device Warranty, but at $37 dollars you wouldn’t be risking much.
Google publishes the EOL dates for every Chrome device on its support center here. You can use this to find upcoming devices which may drop in price and grab them before others do.
You can review this list as well to find devices which are close to its EOL.