Sure you can use .htaccess, that works too. But from my experiments it only works with embedded mode. So you may lose some benefits of the daemon mode. But that's a good question and if you ask the list or search around a bit you'll surely come up with something.
According to the docs WSGIScriptAlias directive only works in a vhost container or server wide (globally).
To do mod_wsgi in embedded mode using .htaccess you can use something like this.
# Skip the media dirs
RewriteRule ^(media/.*)$ - [L]
RewriteRule ^(admin_media/.*)$ - [L]
# Rewrite everything else to disptach.wsgi
RewriteRule ^(dispatch\.wsgi/.*)$ - [L]
RewriteRule ^(.*)$ dispatch.wsgi/$1 [QSA,PT,L]
Of course you need to tell apache what to do with .wsgi as well by adding these globally:
LoadModule wsgi_module /usr/local/apache/modules/mod_wsgi.so
AddHandler wsgi-script .wsgi