For me it is important to know if a client is in the PC version or mobile version.
Search the file footer.php Mobile version
require(DIR_WS_INCLUDES . 'counter.php');
Add below
require(DIR_WS_FUNCTIONS . 'whos_online.php');
tep_update_whos_online();
Thus will on whos_online admin who is viewing the products and that version. Just look at the difference between product-p-123.html and product-mp-123.html for instance.