Thanks to the development of communication technology, trekking in the Himalayas is no longer a journey where all the threads that connect you with your family and loved ones are temporarily cut off. There are more than a couple of ways available for you to stay in touch with the rest of the world while enjoying the thrills and adventures of trekking and climbing. Recently, mountaineers have also successfully used wireless internet atop Mt. Everest. So you can easily assume that you have internet and phone facility in most of the tourist destinations you go. However getting an access to them can be more expensive than you would otherwise think.
If you have roaming services with your mobile service provider back at home, you might also be able to use it. But it will be expensive. You can easily buy a cheap cell phone and Sim cards in Nepal. A cheap cell phone can be bought at around 2000 Nrs and you can buy a Sim card for 100 NRs. In case you like to travel with your laptops and/or tablets, you might find wireless internet connectivity in many places as well. You can also buy an internet data card that will allow you to use internet on your laptop/tablets easily. Nepal has a postal service too. However you will quickly realize that it might not be the best way to stay in touch with your loved ones as it is poorly operating.