Does every waiter needs an iPad?
No. OIDO uses the mobile phones of your clients for order and payment.
All you need to run OIDO is a device in the kitchen and one at the bar.
In smaller restaurants a laptop, all in one screen or iPad /Surface could run at the bar. iPad/Win/ Android tablet in the kitchen.
In larger restaurants a Mac Mini with large screen and washable mouse in the kitchen waiter's area or any number of iPad/Win/ Android tablets at each station (Bar / Desert / Kitchen stations).
Powerful computers are only needed in the kitchen in case of 250+ orders open at the same time.