Is anyone offering live streaming video of the wedding? I'm looking at local companies' packages, and I see one here that offers it for $749. I wonder how many people order that.

Check the Website: Video Production | Green Screen | Live Streaming Studio - Salt Lake City Studio (http://www.saltlakecitystudio.com/)

the problem with live streaming for wedding is you never know if you will get a decent connection on location. And if you offer that, you better to be sure it works.
there are free service like justinTV or Ustream allowing streaming to a lot of clients, just for free, from an iphone for example. So you will get a hard time to sell high something advertised for free elsewhere.
And this adds a total change to the way you will shoot the wedding.
cameras will need to be wired (or wireless) to a mixer, so you can send the feed to an encoder (mainly a PC) linked to ethernet. So, more equipement, more people, more time and you could discover the overhead on the project is well over 750$.
Good 3G connection could be ok if customer is not too finnicky about video quality, but if customer pays 1k$, it is pretty sure he will ask for the best quality possible.