Seems to work, I dropped an .htaccess into the admin directory and added this code:
I tried accessing it from my iphone and all I got was a "oops page not found" error, whereas, my pc was still able to access the directory. Of course, your IP address must be static and not dynamic. Also, I know I could change the name of the admin folder in the gsconfig.php file, however, this is a much better measure against someone brute forcing the admin login.
Code:
AuthUserFile /dev/null
AuthGroupFile /dev/null
AuthName "Example Access Control"
AuthType Basic
<LIMIT GET>
order deny,allow
deny from all
allow from [insert IP Address]
</LIMIT>
Todo arde si le aplicas la chispa adecuada.