Usually found in shops for the purpose of scanning a product's barcode, so a customer can determine it's price before purchasing it. These usually seem to run Windows CE systems on MIPS or ARM architectures, although sometimes, they run Linux or even Android.

This is what runs stock on these devices, without much difficulty. If acquiring one, getting into the underlying system is probably simple, as there's many social media pictures showing one of these things sitting on a CE desktop.

https://www.barcodesinc.com/aml/kdt900.htm

There’s plenty of online examples out there of these things on the WinCE desktop, or with an app, quite like the AML above.