Exchange 2010 - Email signature setup with Transport Rule - Want to disable the rule for iOS devices

So we decided to have a company wide email signature which pulls user info from AD to fill in the HTML template. What I have found out is that iOS devices send email as plain text which displays the HTML content with strings of text in emails send from those devices. The only way I have found to make this work is have the user keep the default "Send from my iPhone" signature and exclude the rule based on that text in the body. Is there a cleaner option in case our users decide to change their default signature on their iOS devices?