Probably better to use candles instead of median price, and set it to show a longer history, for perspective.
http://bitcoincharts.com/charts/bitstampUSD#rg60zigDailyztgSza1gSMAzm1g200zm2g25zxzvWe're currently below the SMA200, and it is probably a significant (moving) resistance, so breaking through form below would be bullish. But note what happened around June 1: we broke through, closed above it (i.e. one day ended while we were above -- note that closing is less important in a 24h market than in a market that actually closes, but not entirely meaningless), but fell back below it regardless.
So the answer is: don't trade based on that alone. If you're interested, find some online resource (or probably better: a book) on TA, and you'll probably find moving averages as lines of resistance/support in general, and the the SMA200 in particular covered. But there is no single "magic" indicator signal you can slavically follow. If there would be such an obvious one, it would be broken through use and become unprofitable in no time.