You don't need any specialised equipment to use Sentiment. A tablet or phone with an internet connection is it. 

As long as that is available you can place the tablet or phone in a place where the customer can see and tap it. Or you can hand it to them when you're packing their bags and ask them to give you a rating anonymously.

Stands and Enclosures

While some businesses will be happy using a simple stand or handing the device to their customer, there will be many who need a more secure and robust solution. These are widely and cheaply available and take a range of forms.

Which stand and whether to use a tablet or phone will depend on what suits you. If you have plenty of counter space then a tablet is more  visible. But if you are lacking in space a phone will be a better fit.