I've looked into a LOT of these booking scripts,... many aren't suitable for mobile businesses that only want to accept bookings from certain area's on certain days, and the few that are can be very limited in the important features like social integration - - after trialing about 30 different systems I personally chose
www.bookeo.com.
There is a monthly fee for using it,.. but its worth every penny IMO,.. especially when it comes to getting customers to "Share" their booking with their Facebook friends (You can offer a small discount to those that share if you want) which can open up a whole new bunch of customers that wouldn't have considered using your services previously.