You need insurance, and this is compulsory if you’re undertaking any adventure activities. This can become very important if a member of your party falls ill and needs helicoptering out of the mountains. Most insurance policies have very strict conditions on what activities you can and (mostly) can’t do. We can safely recommend Nomads for worldwide residents and Trailfinders, but only for residents in Europe. Please check the details on Adventure Activities at Nomads and Trailfinders cover at either site and e-mail them if necessary.
If you’re living outside the West you may get much better quotes from local insurance companies, just check that you’re covered for going to the height that you’re going to go to, with maybe using ropes, and any other activities that you might partake in, eg paragliding. And I should get it written down that you are covered as said, though the only problem I ever had was with a UK company rep lying to me.