Some very simple techniques have been discovered to allow the Orange SPV Smartphone to run unsigned applications. Basically it involves making a couple minor changes to an xml file, hard resetting the phone, and tricking ActiveSync into allowing you to copy the modified files to the phone before the PIN is entered.
Obviously this requires modification to the client's phone, as opposed to the 3rd party applications themselves. At the very least it provides a method of using the hardware for software development.
The specifics are in this large thread:
http://www.modaco.com/smartphone/viewtopic.php?t=1899
Dan East