I feel that a lispy language on the ipad should not be text-based, but tree-based: you create and manipulate the tree structure using the touch interface.

For example, you touch, and that creates a node.

   o

Then you can type something inside that node. Then you drag lines out of it, and you create child nodes, and so on.

    o-------o
     \
      \
       o

The node doesn't have to be a circle, it could be a long rectangle with atoms inside

   [  ____   ______    ______ ]

You can drag out an atom to turn it into another node

   [  _____   ______    ______ ]
        |
        |
        |
        |
   [ ___  ___ ]