K9 on Android isn’t much good, TAG don’t recommend it. There are alternative filters and app lockers for Android which, combined in the right way, allow the phone to have filtered web access. They can be locked down almost as effectively as a iPhone, neither are 100% foolproof.
K9 filtering on the desktop is, despite many claims to the contrary, the best overall filter but the mobile version is nothing like the desktop one and should rarely be used.
If K9 do produce a filter for Blackberry, I wouldn’t trust it either, and doubt that a good filter will come out for the Z10 for quite a while. Blackberrys, both old and the new Z10 do allow you to block the browser altogether, but having filtered web (i.e. you get to use the browser but sites are filtered) on Blackberry is far more complicated, especially if you don’t want to pay a monthly fee.
OP: If you care about filtering on mobiles, then call TAG or Venishmartem.