When going into remote areas, it would be great to be able to communicate with the outside world, for emergency purposes or just to be able to call home on long trips. Is it practical for an average person to obtain and use a satellite phone? In other words, roughly what do they cost to buy or rent, how large are they, and what is the cost to use them to place calls? On what kind of trips would it make sense to consider this option?
What is practical is up to you, but I can give you some information to help you make up your mind.
Typical rental prices for a satellite phone are $15-$30 a week (According to this site). The cost per minute is in addition to this cost, and is around $0.50-$3 USD a minute. Weight is usually around 400 grams, or just under a pound. Battery life is pretty much comparable to a smart phone, 3 hours talking and 24 on standby.
In addition to @Pearsonartphoto's technical specs, it is important to remember that a Sat Phone is one tool at your disposal, and not a replacement for smart decision making, or proper planning. I have seen them provide people with a false sense of security thinking it gives added insurance against making bad decisions.
Like any electronic equipment, sat phones depend on batteries (which don't last all that long), must be kept dry, and can not be depended upon. (Ie, assume it will be broken / dead when you need it.)
I have been required to use sat phones extensively in the back-country as part of my work responsibilities - in both the mountains and canyon country - and they have proved extremely useful, if frustrating. Getting a signal can be challenging and talk time is short (as satellites whizz by above) possibly to the point of miscommunication: ("Hi honey - I'm ....." "Oh my! what's wrong? Did she break her leg? Why was she cut off?!? Panic!")
All that being said, having a sat phone saved at least one life I was responsible for.
You're almost certainly going at this the wrong way. For something like this you want a Garmin inReach unit--the costs are a lot lower. They only give you text messaging, no voice communications.
There are also the SPOT units, I'm not sure about their messaging capability. There are also some smaller players now entering the game, I don't know the details.
Finally, purely for emergency use there are personal locator beacons. They have no messaging capability, when triggered they send out a generic HELP! The advantage is there is no monthly cost. (Although you do need to replace or refurbish your beacon every 5 years.)