Nice intro to the ability to send text messages via satellite from the SPOT transmitter in the NYT today. The capability helps you keep in contact with the outside world when you are beyond the reach of cellphone towers. So while the walk in the park might keep you in contact with even an AT&T network tower, a walk in a National Forest might get you so far out that you need something like the SPOT.
We've talked about the DeLorme PN-60W GPS receiver that gets you out there and pairs with the SPOT transmitter to send SMS messages and location statuses via the SPOT transmitter. In the first quarter, SPOT is also going to release a smartphone App that will pair with a special "SPOT Connect" transmitter to send messages. The video below describes the service that is supposed to launch imminently.