With GoTenna, 'No service' is no problem. This is what there official website says about this new device named GoTenna. GoTenna is capable of connecting the smartphones even if they are not in the coverage of any cellular service provider, Satellite or WiFi. They do it, by creating a communication channel using long-range radio waves. A GoTenna which is connected to your smartphone (via a Bluetooth connection) will communicate with another GoTenna (connected with the recipient's smartphone) available in its range to deliver your message.
GoTenna is accompanied by an app which needs to be installed on your smartphone (either Android or iOS) in order to communicate with other devices. You will be able to send a message (to an individual, or a group or broadcast it to anyone in the range with GoTenna) and share your location on detailed offline maps using this device. You smartphone should be in the range of 20 feet of a GoTenna to maintain the Bluetooth connectivity and it has been claimed that a GoTenna can communicate with another GoTenna within a range of 50.5 miles. However, this distance may vary as per the terrain in which it is being used.
So, next time you are planning to go for a trek with your friends, then this device will really come-in handy. You will be able to be in touch with your friends all the time. Once GoTenna is fully charged, it will last for 72 hours when it being used continuously and while being switched off it can hold the charge upto 1 year. Its 'Shout' feature is also very useful, especially when you are in a need of urgent help with anyone available in the vicinity. It will broadcast an emergency message (along with your location) to all the GoTenna users available in its range.
This device is really portable and can be really useful in case of emergency. At this point of time, you will be able to pre-order your GoTenna pair at 149.99 USD (yes, they are sold in pairs because only one is useless) and it will be available at the price of 299.99 USD after this 'Early Supporter' offer ends. Currently it is available in 2 pairs of colors, i.e. Green & Blue and Purple & Orange.