It's a good idea to have a couple mouth calls handy in the event your e-call fails for any reason.
In my opinion, an open reed call is a must. Closed reed calls freeze up fast in this kind of weather. I like my Foxpro Skyote call a lot. Very versatile. I'm also in the process of learning how to use my primos diaphragm call. Hands free and makes great ki-yis when mastered.