If you are a busy salon then you probably want to use some POS hardware such as a receipt printer or cash drawer. Many web based appointment systems offer no kind of integration at all, struggling with the unique challenges of a browser based application. You'reOnTime offers integration with Receipt Printers, Barcode Scanners, Cash Drawers and Card Swipers.
In the US we recommend Barcodes Inc and you can purchase hardware packages from http://www.barcodesinc.com/bci/part-yot-standard-pos-system.htm
In Australia we recommend this great value package http://www.microtrade.com.au/pos-hardware-pack-with-thermal-receipt-printer-cash-drawer-scanner/