How much can GPS on a phone actually do? Meaning lets say I get stranded on a deserted island or lost deep in woods, and there is no cell phone service. Then if all you have is GPS, which should work I assume, is there any way you can send communication back through satellite to get help? Like what

No, you can't send any "GPS" signal back without a proper transmitter. GPS can only help you find your way. You will need wireless (Wi-fi), G3/G4, or some other way to send your coordinates fo rhelp.

GPS is a broadcast only service. This is a common misconception. You can't be "tracked" unless another system (cell, etc) is being used to share your location.

Unlike most other radio access technologies, GPS is unidirectional. You can only receive signals; not transmit them. So, to answer your question, there is no way you can use 'only' the GPS on your phone to communicate with the world. Just to be fair to not undermine the ability of GPS as a life-saver, E911 tries to identify the caller's location using GPS. Also, if at all I get lost in some unknown territory, I would use the GPS to move in the direction of a water body/vegetation to search for signs of life :-).

Your GPS can actually do a lot more than you could ever imagine. For drivers stuck in emergencies, or no internet zones, there are smart options that can totally save your soul. If you haven't try GrayDrop (http://graydrop.com), a solution that comes with SOS-navigation. Whenever stuck, use it to send your location details to someone, or retrieve driving directions to a safe location - all without internet. You don't really need to tap into the satellites in this case, when even a very weak telecom network service can be so useful.

1. GPS satellites are http://www.thefreedictionary.com/continuously broadcasting the signal(Orbital info + Time info).And there is no option to recieve the signals/ messages from GPS receivers. So Just we will get the current location information, when are you in remote http://areas.No way to share your location information.

GPS Navigation chipset in your mobile phone is a radio beacon receiver. It receives signals from a minimum of three satellites to calculate the position of the handset using Pythagoras theorem and good 'ol trigonometry.  It does not send anything back to those satellites orbiting at 20,000Km from Earth. You would require a terrestrial GSM connection to send the position information. The alternative is to have an Iridium or Thuraya Sattelite Phone that would relay your postion to a terrestrial network. Container tracking services use Satellite Thuraya or Iridium networks to relay position information. Due to the high costs of Sat com these are relayed usually at low frequencies (every six hours or once a day).

Having a GPS in hand is anyways useful. The smart phone GPS without cell phone signal would still work. However. It would take around 10 mins to get the first fix. You wwould able to get the coordinates of the place but without any under lying map. ( map is a function of the data provider, but if u have a stored map or cached map you might get). So you would be able to get your location exactly. Coming to the second part, you will not be able to transmit anything without signal. The only way of doing that is by using a satellite phone which is not dependent on cellular signal. So if you are caught in an isolated place , you can use your GPS to navigate to the nearest place of civilization.

GPS is a one way broadcast system for all practical purposes - like a FM radio station. You cannot send anything to the satellite just as you cannot use a FM receiver to call the radio station.