Billings Pro

Billings Pro is a powerful multi-user time tracking and invoicing solution for the Mac and iPhone, with a Web interface called Timecard for non-management staff.
Billings Pro was built for service-based small businesses with 1 to 50 users, and offers a unique solution for the utmost flexibility.
With Billings Pro's flexibility, you can track time, expenses, and mileage from anywhere at anytime.

For small businesses, losing track of as little as 3 billable minutes a day per employee can equate to thousands in lost revenue.
Billings Pro is a subscription-based service. Free Account - 1 invoice, 1 estimate and 1 statement per month Freelance Account ($5/user/month) - 5 invoices, 5 estimates and 5 statements per month Professional Account ($10/user/month) - unlimited invoices, unlimited estimates and unlimited statements per month Professional Yearly Account ($99/user/year) - Same as professional plan pre-paid for a year ($21 discount)
For full pricing details, see here.