A not-so-hidden feature in iOS is the ability to add extensions to phone numbers (most relevant for business) that will be auto dialed after the call is picked up. When entering the number into the contacts information, hit the “+*#” button in the lower left of the dial pad and you will have an option to add a “Pause” or a “Wait” to the stored phone number.
Here is apple’s documentation on the features: http://support.apple.com/kb/HT4515
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