Currently I am working on an iphone app that lets user create templates, and when it's time to send an email or SMS, the user can select a template, fill out some fields (or check some check boxes), and send it.
The template accepts text variables and expressions. Expressions are infix expression with the option of parenthesis, which are calculated upon sending the actual email or SMS.
The app is still in an alpha status, so there are many features that I cannot disclose just yet.
The template would look like this:
Happy New Year, {@name}!{{{#Number Of Products}*{#Product Price}*(1+{#Sales Tax})+{#Shipping Fee}}}