Yes.
They also have a more expensive option which can be turned on and off at any time:
Tarieven mobiel internet in het buitenland met Travel & Surf - T-Mobile it gives you 100MB at unlimited speed and then throttles to 64kbps. €14,95, valid for 1 week.
This option is actually also available for prepaid customers, but for prepaid it isn't unlimited (after 100MB you pay the full price again).
Oh, and there's also Vodafone, which has a day package of 35MB for €2, which also includes 20 incoming minutes, 20 outgoing minutes and 20 SMS. So this would also be a little cheaper than Medion.
Alles-in-1 op Reis