online to-do lists

I've been keeping my to-do list in a text file on my phone, and that together with my phone's calendar and my email are the things that pretty much run my life. Someday I'm sure that there will be a way to have all of those things integrated the way I want, most likely through an online service. To do so, they'll have to:

• make it easy to make notes wherever I am, ideally with Jott
• allow me to attach a "context" (and a time estimate)
• integrate with a calendar
• allow for task dependencies

Today I figured it was time again to check around and see if today is that day. It looks like it's not. The dependency feature is the hardest to find, and I'm a bit surprised it's still not very widespread. Here's some of the info I've gleaned from about a dozen sites:

• For a comparison chart, see ToodleDo
• The only one with subtasks that's free (from ToodleDo's chart) is Todoist.
  
• Jott ties to multiple other services, but working with the to-do-list sites requires a paid subscription (minimum $3.95/mo)
• The only one with full collaboration that's free (from ToodleDo's chart) is Remember The Milk, though 4 others have it as "partial"; Hiveminder claims to have it too
  
• For dependencies, I only found it in Hiveminder (in this explanation), which appeals to the developer in me (because it implies that I can do other things with it programmatically). Most places suggested to create a new list/folder to manage this. (Oh, and Hiveminder integrates with Jott now. Hm.)
  

Remember The Milk is integrated with Jott for free, which makes it most attractive for a trial; I'd like to try Hivemind for their dependencies, and I will if I do a paid subscription to Jott (eg. pay-as-you-go, because Jott is critical but I use it rarely).