The 'trick' is to find a unique part of the user agent string to add to the Custom area. For example if it reported:
HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 6.0; Windows 98; PalmSource/Palm-D062; Blazer/4.5) 16;320x320
You'd guess that eitehr
Palm or
PalmSource or maybe
Blazer would be unique to mobile devices, so you could add one or all of them
or with
Opera/9.80 (J2ME/MIDP; Opera Mini/4.2.14912/756; U; en)
Presto/2.2.0
You maty want to try
Mini or
Presto (as it turns out,
J2ME and
MIDP are already keywords - but doubling up doesn;t have any bad side effects)
All this mobie detection stuff should really be posted over here:
https://vborg.vbsupport.ru/showthread.php?t=173239 as it has nothing to do with this style.