I'm a little confused. Are we talking about true
WAP/WML, or cell-phone-sized html pages?
My cell/PDA pages are straight html, or php-generated HTML, and they show up fine on my Verizon Moto E815 phone and Dell Axim. About the only problems I have found are:
1) The phone doesn't display PNGs. A little PHP to convert my PNGs to JPGs fixes that, and it's probably not a WML vs: HTML problem. (Xtide and findu.com APRS CGIs make PNGs, so I have to convert them.)
2) URLs are a PITA to enter and save on the phone. Again, not a WML vs: HTML problem. I dealt with that by creating a SLOweather phone portal, save that URL on the phone, and then edit that portal page to add any links I want to see on my phone.
They also seem to work OK on ATT/Cingular/iPhones. I see a lot of mycingular in my stats, and I've seen it displayed on an iPhone.
Now, if I could only figure out how to make my SLOWeather cell page my phone's home page, I'd have it made.
Dunno for sure right now about T-mobile, but I think I've seen it in the stats before. I'll have to check.