Text Widget in Footer for just 1 page template

There are a couple of options:

1. Use a Plugin that adds contextual conditions to Widgets

2. Only output the dynamic_sidebar() in the page template in question. For example, if your custom page template is named template-foobar.php, and the dynamic sidebar name is footer-text-widget:

   if ( 'template-foobar.php' == get_page_template() ) { 
       dynamic_sidebar( 'footer-text-widget' ); 
   }