// be sure apache is configure for the .wml extensions! 
// put this function somewhere in your application, or in Smarty.addons.php
function insert_header() {
 // this function expects $content argument
 extract(func_get_arg(0));
 if(empty($content))
 return;
 header($content);
 return;
}

// your Smarty template _must_ begin with the insert tag example:

{insert name=header content="Content-Type: text/vnd.wap.wml"}

<?xml version="1.0"?> 
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml"> 

<!-- begin new wml deck --> 
<wml> 
<!-- begin first card --> 
<card> 
<do type="accept"> 
<go href="#two"/> 
</do> 
<p> 
Welcome to WAP with Smarty!
Press OK to continue... 
</p> 
</card> 
<!-- begin second card --> 
<card id="two"> 
<p> 
Pretty easy isn't it?
</p> 
</card> 
</wml>