These are few and far between at the moment.
You might want to look at the Samsung Gear S (http
/www.tomsguide.com/us/samsung-gear-s,news-19426.html), which you can probably find through your wireless carrier. It has a slot for its own SIM card and can use 3G data. It's not one of Tom's Guide favorites, but it is a standalone watch.
The LG G Watch Urbane LTE has the body of the Urbane but has, you guessed it, full LTE capabilities. It doesn't, however, run on Android ware like the regular Urbane. There's no set release date for this one in most countries, though.