Hi Bertrand - looks like a very promising package, glad to see it. One question - is there any chance the /:variable notation could be changed to /$variable as :variable is a ruby construct that doesn't make sense in PHP.
It's more like SQL "bind by name" (see PDO documentation <http://fr.php.net/manual/en/function.pdo-prepare.php> for an example). I think it's safer to use ':' than '$' especially if someone has an insecure php.ini configuration (register_globals) and/or uses double quotes to set the routes.