My name is Giada, I am with the Support Team at Shopify!
You can use Shopify's Point of Sale (POS) system for your Chauffeur business. Shopify's Point of Sale system is available for businesses that are located in Canada, the United States, Ireland, and the United Kingdom. Depending on where your business is located, there are some differences in products that are available. When it comes to the card readers, when you click on a card reader in our Hardware Store each product page will have information about what device is compatible with that particular card reader. Our Point of Sale system takes payment when connected to the internet. Because you may not always be near a wifi connection, you can process payments when the data on your device is turned on. You may want to contact your mobile provider to be sure that you are on a good data plan because if you are going to be using your data consistently, it's good to ask your provider if they have any deals on data plans - you can save quite a bit of money by price comparing mobile plans from different companies.
Best Wishes! :D