I used OmniFocus on the Mac and the email rule setting along with an address book entry to make it easy for Siri to create OmniFocus items. Now I can say something like this to Siri:
"Tell Omnifocus Pick Up Books At Library"
And it works.
Here's what I did:
1. In OmniFocus on the Mac, use the OmniFocus Preferences to turn on a Mail rule, allowing for the from address in emails sent through the AT&T SMS gateway (in the form
2125551212@mms.att.net)
2. Double check the new email rule in the Mail Preferences
3. Create a contact with the first name "Omni" and last name "Focus" (it had a hard time when I created a contact with the name "omnifocus". Set the email address for that contact to be
youremail+omnifocus@yourprovider.com
Thus, when you say "tell omnifocus" to Siri, it'll create a text message to send to that address, which in turn, when received, will trigger the mail rule to create an omnifocus item. It's a little bit convoluted, but doesn't require AppleScript hacking and works well for me so far.
Hopefully, the geniuses at Omni Group will come up with a more elegant and general solution soon, but in the mean time this will do.
p.s. If you don't want to use SMS, you could also say to Siri: "Email Omnifocus..." but this requires an extra step to fill out the email message body.