While there's a lot to be said about planning ahead, if you're just wanting it for emergencies and the whatnot then there's another option, depending on how comfortable you feel and how much time you want to spend.

Wait until you get there.
Go down to one of the ubiquitous phone shops and get the cheapest phone you can find. (Just took a look on amazon.de and you should be able to find a used nokia for under €15)
Buy the cheapest sim you can find (in Ireland many will even give you free credit, check out Meteor or 3)
Charge the phone up overnight
Good to go.

Alternatively, if you have your first night's accommodation booked, you can ask them if you can have something delivered and get the cheapest phone you can find on Amazon or some place similar sent there. Then you don't even have so much a language barrier if one exists.

I know that at least this worked the last time my parents were over, and they said it was easy enough.