In addition to the "rough air buttons" available in CV's Bluetooth
version, another option is just to pull the pda out of the cradle, do
what you need to do, then park it back in the cradle. If you have a
competent autopilot that you trust to drive for a minute in rough air,
using 2 hands works well.

If it's really rough, though, I find it difficult to operate ANY device
in the airplane that doesn't have a large handle on it.

The XM activation problems that CV has been having are apparently a
problem with all XM users because of the way XM handles activation.