Oops, just saw this question now. I've registered with https://www.otelo.de/ after seeing their publicity on TV two years ago and they still seem to have available these promotions.

They have several phone models to choose. You pay 1 EUR for most models from Samsung or Sony, a bit more for the deluxe editions (iphone and sorts). Now they even offer more because SMS are free and I still pay extra for each one, but doesn't matter because I simply use other messaging apps.

The Sony Xperia models are good, they're waterproof by default and resistant to shocks, albeit camera is crappy (compared to normal Samsung models)

I pay 12 Eur for unlimited calls/sms within Germany; 3 GB data; w/o phone; w/o contract term (it can be canceled any time); 100min and 100MB free in other EU countries.

They exist. Even prepaid options are getting cheaper. Take a look at discounter offers (Aldi, Lidl etc). Though don't expect great network coverage on the countryside...