SymPy is now divided in 3 packages :

python-sympy (python section)
python-sympy-ui (interactive shell, with isympy and an icon)
python-sympy-doc (doc section)

I have succeeded to promote python-sympy, python-sympy-ui and python-sympy-doc to extras-testing on Maemo 5.

On Maemo 4, python-sympy and python-sympy-doc were promoted from extras-devel to extras. python-sympy-ui is not yet released to Maemo 4 due to an old version of iPython which is incompatible with isympy, so I will try to release iPython 0.10-2 to Maemo 4/5.