Simple way to allow yourself the convenience of editing a live development theme where you want some privacy while working out a bug etc. Just drop this into functions or a plugin and include your IP. Works great.
$developers_ips = array(
"255.255.255.255",
);
//check if the visitors ip is inside the list of developer ip's
if(in_array($_SERVER['REMOTE_ADDR'], $developers_ips)){
//theme visible to developers
switch_theme( 'theme-directory' );
} else{
//theme that's visible to the public
switch_theme( 'theme-directory' );
}