This is more or less how I've been handling my work as well. Didn't know there were systems describing it. I use Asana, it's not perfect but it works.
What I was looking for, and couldn't find, is a personal productivity tool in the same category as Wunderlist, Todoist, Swipes, Things and countless others, but with much stronger todo de-cluttering abilities.
Also, I think that a proper todo app, in addition to geofencing, should include timefencing, people-proximity-fencing, external-condition-fencing and maybe even mood-fencing / energy-fencing. Though I guess some of these can be implemented via contexts.
I grudgingly switched to Asana a few months ago and haven't looked back. It supports a GTD workflow with the addition of excellent communication and integration with other tools. For example, I automate task creation with Zapier to follow-up on calendar events in my diary, follow up website leads, scanned biz cards, etc. Placing tasks in multiple projects is also super useful. Omnifocus still has a better mobile app UX, and I wish it would offline sync to make better use of precious planning time on my commute.
The part of this post that I already found useful in the few hours since I read it is adopting the Pomodoro time management technique. I found a neat OS X app that called PomoDone (http://pomodoneapp.com/) that syncs with Asana and many more task managers to keep focus in 25 min intervals followed by 5 min breaks. Thanks!
As I've grown from lead developer on a 3-person team to CTO of a 40-person company I've had to get more serious about my GTD practice. Where once I had several inboxes: OmniFocus for personal/recurring tasks, then Gmail, Pivotal, GitHub and Trello, now I've doubled down on OmniFocus as the source of truth for my workload. That doesn't mean projects are managed there, only my personal tasks related to the project that will take longer than 2 minutes make it there. Chucking things into OF from many different sources becomes very easy with Quick Entry and Clippings tools, and it is invaluable for planning each day and making sure things don't slip through the cracks. Typically I'm collecting things in OF all day and flagging important things, but at the beginning of the day I actually set a Focus on work projects, and write out in my notebook the list of priorities for that day. I know GTD is all about getting away from re-writing lists, but I find it helpful to have a hard copy of my foci sitting in front of me that doesn't take up screen real estate is impervious to the daily influx of distractions.
Basically, if you tell siri to remind you of something, it creates a task in the Reminders app. OF imports this, including due dates.
What I really like is ability to break list in what I call 'milestones'. Also adding from email is surprisingly useful.
In the end, I just can't use it, because I need to shuffle things around and Asana doesn't seem to support that.
-It's just me (Asana is meant to be used with a team. That's not how I use it.)
-I don't split up projects in to Asana 'Projects.' I make one Asana Project for each client that I work for and a separate one for 'Personal'. I split up real life projects in to Headings with subtasks in the same Asana project. (All projects for Client A go in the Client A project.) This way I'm never trying to move tasks between projects.
-As tasks come up that I want to remember, I forward them to the email address for the correct Project (client). I usually change the subject line to be more descriptive of the task. This puts them at the top of the list for that client.
-In between tasks (usually every few hours while I'm working) I read over the list and categorize anything new that I've emailed in under the right heading. I also set the due-date to be the next time I want to work on that particular task.
-As I get started for the day on a certain client, I'll look at the list for that client sorted by due date and try to cross off or reschedule everything for that day.
-Sometimes I'll tag tasks with a name of the person I need to talk to or the location that something needs to be done. That way the next time I run in to JohnDoe I just say 'oh hang on I had a few things to talk to you about' then tap tap tap to the JohnDoe tag in Asana.