UI is most important, should be modern, simple and easy to use. Must have all the required features for a restaurant or cafe. With web backend to manage, add/edit items, generate reports, etc. Manager App will be a plus.
Should easily connect with all hardwares, such as printers, etc.
Preferred language for main POS is C# or VB.Net, PHP for Backend and for Tablet Menus (Ionic/Phonegap)
But It's not necessary. As long as you have the right software, no matter the language. I will be interested.
If you have such a product ready, please send me demos and I will buy the best one. Thanks.