For Class based gyms, use our Check-in app on a tablet mounted to your front desk, however, if you just run an open-gym type scenario where you do not need to track attendance by class but simply verify if the member has a valid active plan, you can issue them barcode cards and scan with a USB barcode scanner connected to your front desk computer.
Any USB barcode scanner should work. Available for around $20.
Any plastic card with sequential barcodes between 6 and 12 numbers.
Here is one option to order custom barcode cards.