here is what works for me:
1. in outlook I use Netcentrics GTD plugin where the GTD contexts seem to be mapped to categories.
2. on my iphone I use IMEexchange and sort the tasks by category which is the same as looking at a context view.
Limitation is 'no project/subject view'
I agree with other that omnifocus is better and I use that with my personal Macbook and the same iphone.