Using your iOS or Mac products with mobile satellite services is indeed possible.
1. You'll need a satellite phone or terminal.
2. A way to get the satellite data to your device (either a USB cable, ethernet cable, or in the case of iOS, a satellite Wi-Fi device.
3. Specialized software to deal with the slow data in the case of handheld phones, or to block unwanted data in the case of satellite broadband terminals.
Handheld satellite phones that have verrry slow data, but fast enough for email, downloading weather data via GRIB files, and specialized web-browing. At 2.4 kbps to 9.6 kbps (many times slower than dialup service) they won't replace any other wireless, but they work virtually anywhere you can see the sky. You will need specialized hardware and software to use it. There are satellite Wi-Fi routers from Iridium (AxcessPoint) and GMN (Optimizer). if you're using iOS, you'll need an app that is designed to deal with the slow data http://itunes.apple.com/us/app/xgate/id490417552?mt=8
"Satellite Broadband" terminals (basically Iridium OpenPort or Inmarsat BGAN and FleetBroadband) are much faster than the handhelds, and very expensive compared to cellular. Again, if you need data where there's no cell coverage, they're great. Just know what you're getting.
Those warnings aside, it amazes me that you can stand anywhere in the world with nothing more than an iPod Touch, a handheld satellite phone and a little satellite wi-fi box and be able to send/receive email.