It is critical that you have an easy way to communicate with the rest of the world wherever you happen to be. Whether you are driving home from work or on a camping trip in a desolated area, you should be able to call for help or call your friends or family to update them about your location.
If you are out on a nature trip in an isolated forest or lake, there is only a remote chance that you are going to be able to get decent cell service. Therefore, it would be easier to have something like an Inmarsat Isatphone that you can use wherever you are and ensure that you get a clear connection as soon as you need it.
Having access to an iridium satellite phone is also a good thing if you happen to be in a foreign country and get caught in a political upheaval. If you are taken captive, finding such a phone may be the only way that you are able to call for help either from your embassy in the country or to your friends or family back home.
Having access to an easy method of communication could be what helps you survive when you are stuck in an emergency situation. Whether you are being followed on the highway or are lost in the wilderness, you may only have minutes or hours to find help. This means that you should keep a satellite phone in an emergency kit that you keep by yourself at all times.