I'm looking for a time recording system for a small team (8-12 people) for a three month project. I'm hoping the members here may have used something suitable they can recommend:
 - Must be software as a service - we don't want to host it
 - Must allow a common set of activities for all staff.
 - Should (almost must) have an Android app that will let you start/stop your time, as well as a web interface where time can be manually entered.
 - Could have an Apple app as above
 - Must be easy to use
 - Must produce a variety of reports (management level, detail level)
 - Must be able to get up and running very quickly (ie less than a day), ideally self administered with low complexity. We'll favor simplicity over functionality.
 - Could allow for nested tasks. For example we may have a parent task "project work", with subtasks "project a", "project b", etc. Upper management may want to report on "how much time did the team spend on project work", individuals may want to say "how much time did I spend on project a".

Cost is not really an issue, within reason.

Freshbooks is one thing we're considered, but it doesn't have nested tasks as far as I can see. Any other ideas?