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/