I think the best way to explain my suggestion is an example:
Task: Call Ms. Smith 012-345-678
With a Tap on the Phone-Number you should be able to start the Call.
Same for E-Mails:
Task: Send Tim the newest reports firstname.lastname@example.org
With a Tap on the Mail-Adress you should be able to open Mail.app
You can already do this by entering the phone number ( xxx-xxx-xxxx ) or email in the "note" section of the individual task or project. One of the developers did this on the fly during the early days of this program, in response to an email request. I agree that it would be great if the same thing occurred on the fly in the task creation main title, instead of a second step. Also, the web app doesn't do either, and would be a huge plus for outside email contacts.