Always carry a phone away card, you never know when you're going to want/need one!! I used to always have one in my headset bag just incase.
As others have pointed out you always have your phone/ipad/laptop etc... Worst case scenario, grab ATC on the radio and at least get them to submit a SAR for you, its a quick option, all they want for it is your Callsign, Aircraft Type, POB, Departure and Destination Points and the Time itself.
I was doing some pretty remote stuff not so long ago where we'd be well away from any kind of internet/mobile access and the planned stops always changed with the owners mind!! This meant that I usually did this twice a day and never got too unfavourable a response.
OH and in a pinch, check if theres a Met Office near-by, they're usually staffed by some really nice people who don't mind someone new to have a chat with whilst you plug in a quick flight plan!!