Para adicionar à postagem de Shane Madden, você precisa de algo como o seguinte para redirecionar o site principal para o site para dispositivos móveis, caso ele esteja sendo navegado por um navegador para dispositivos móveis.
NameVirtualHost *:80
<VirtualHost *:80>
ServerName domain.com
ServerAlias www.domain.com
DocumentRoot /var/www/html
RewriteEngine on
RewriteCond %{HTTP_USER_AGENT} "iphone|ipod|android|blackberry|opera mini" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "pre\/|palm os|palm|hiptop|avantgo|plucker|xiino|blazer|elaine" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "iris|3g_t|windows ce|opera mobi|windows ce; smartphone;|windows ce; iemobile" [NC,OR]
RewriteCond %{HTTP_USER_AGENT} "mini 9.5|vx1000|lge |m800|e860|u940|ux840|compal|wireless| mobi|ahong|lg380|lgku|lgu900|lg210|lg47|lg920|lg840|lg370|sam-r|mg50|s55|g83|t66|vx400|mk99|d615|d763|el370|sl900|mp500|samu3|samu4|vx10|xda_|samu5|samu6|samu7|samu9|a615|b832|m881|s920|n210|s700|c-810|_h797|mob-x|sk16d|848b|mowser|s580|r800|471x|v120|rim8|c500foma:|160x|x160|480x|x640|t503|w839|i250|sprint|w398samr810|m5252|c7100|mt126|x225|s5330|s820|htil-g1|fly v71|s302|-x113|novarra|k610i|-three|8325rc|8352rc|sanyo|vx54|c888|nx250|n120|mtk |c5588|s710|t880|c5005|i;458x|p404i|s210|c5100|teleca|s940|c500|s590|foma|samsu|vx8|vx9|a1000|_mms|myx|a700|gu1100|bc831|e300|ems100|me701|me702m-three|sd588|s800|8325rc|ac831|mw200|brew |d88|htc\/|htc_touch|355x|m50|km100|d736|p-9521|telco|sl74|ktouch|m4u\/|me702|8325rc|kddi|phone|lg |sonyericsson|samsung|240x|x320|vx10|nokia|sony cmd|motorola|up.browser|up.link|mmp|symbian|smartphone|midp|wap|vodafone|o2|pocket|kindle|mobile|psp|treo" [NC]
RewriteCond %{HTTP_USER_AGENT} "!ipad|xoom" [NC]
RewriteRule ^(.*) http://m.domain.com$1 [R,L]
</VirtualHost>
<VirtualHost *:80>
ServerName m.domain.com
DocumentRoot /var/www/html/mobile
</VirtualHost>