According to the QMaemo5ValueButton documentation, setPickSelector() transfers
the pick selector ownership to the value button. This requires adding something
like this to the QtMaemo5 typesystem (untested):

    <modify-function signature="setPickSelector(QMaemo5AbstractPickSelector*)">
      <modify-argument index="1">
        <parent index="this" action="add"/>
      </modify-argument>
    </modify-function>

Test case that triggers a segfault:

from PySide import QtGui, QtMaemo5
app = QtGui.QApplication([])
pickselector = QtMaemo5.QMaemo5ListPickSelector()
button = QtMaemo5.QMaemo5ValueButton("test")
button.setPickSelector(pickselector)
del pickselector
print button.pickSelector()