I think with the new phone system, this is almost a moot point. As soon as you enter your MP number, it routes your call appropriately, regardless of what number you call or what phone you call from.

I saved the number in my cell phone, as well as in my online address book (yes, I still use a dumb-phone which does not, in any way, link to my computer). In any case, putting it in those 2 places took minimal effort and ensures that I'll rarely be without the priority number.