Use wamp localhost in other device

If you by wamp mean WampServer 3.0 or later, you activate the "online" feature this way:
1. Left-click => Apache => httpd-vhost.conf
2. Add "Require ip 192.168.0" or whatever your ip-range are to your virtualhost for CI. 

This example are for the document root (not recommended). You should have a virtualhost for CI and have your mobile access the ServerName instead.

Code:

<VirtualHost *:80>
    ServerName localhost
    ServerAlias localhost
    DocumentRoot c:/wamp/www
    <Directory  "c:/wamp/www/">
        Options +Indexes +Includes +FollowSymLinks +MultiViews
        AllowOverride All
        Require local
        Require ip 192.168.0 #This is your ip-range
    </Directory>
</VirtualHost>