Hi Shane,
It's not really a tongue twister for Mandarin speakers, so much as a wonderful play on tones on the same phoneme. It's not hard to pronounce - my definition of a tongue twister - but just a glorious play with language. There's only four tones in Mandarin. [This latter point can be argued a little, but only four tines are common and essential.]
While we are here, David's original phrase is not hard to pronounce for an English speaker at all. It falls into the category of alliteration, which abounds in English, rather than tongue twisters.
Andrew