T-Sheets is a highly rated app that's easy to use, inexpensive, and it tracks time by user and project. Push a button on your mobile device or in your browser to clock in and out, switch projects, take a break. It sends you reminders to clock back in after a break. It tracks overtime, vacation pay, and sick pay. A crew lead can clock in a whole crew. It has GPS location tracking - you can even see the path your employee took to get to a job! The time pushes to employees in QuickBooks. Nice pie charts and exports to Excel.
I'm using this to track my time on projects, including overhead time, even though I don't charge by the hour. It's worth knowing where those hours go, and how long things really take. I use this feedback as part of my business planning.
I joined T-Sheets Accountant program, so I can get you a discount if you sign up through me!