WPtouch Pro 4.3.14+ will send a 'no cache' request in the header of the mobile theme. This is useful when there is server-side caching, like Varnish cache, is enabled. By default, WPtouch Pro sends "Cache-Control: no-cache, must-revalidate, maxage=0" header, which tells Varnish to not cache the page when the mobile theme is visible. If it does cache it, it is valid for 0 seconds.
WPtouch Pro sends the no-cache request in the header by default, but this can be disabled in Settings > Site Compatibility > Caching.