Other places where one can have off-grid experiences are Mountain Hotel Sulzfluh in St. Antönien/ GR, the Mountain Hotel Obersteinberg in the Hinteren Lauterbrunnen Valley, and the simple Pension Spielbodenalp near Mürren.
Road to the Gastern Valley not open to the public, only pre-approved vehicles adsmitted.
How to get there:
Drive or take public transportation from Spiez to Kandersteg, Swiss Post Bus or private car from Kandersteg to Gasterntal. Walk the rest of the way.