The Amoi WP-S1 (sold as the 3 Skypephone in the UK) almost certainly supports Obex over USB, but sets its interface class, subclass, and protocol to 255 (vendor-specific), so is ignored by check_intf() in lib/usbobex.c. OpenObex should be able to work around broken devices such as this.
My WP-S1 talks happily with my Mac over Bluetooth. Examining the protocol it uses when talking to the vendor-supplied Windows client over USB shows a protocol that looks like what I expect Obex to look like. My Linux PC doesn't have Bluetooth support, so I can't check whether OpenObex can talk to my phone over Bluetooth.
It's of course possible that the WP-S1 uses some weird variant of the Obex protocol, and I'd be happy to do any testing necessary to check that out.
The Amoi WP-S1 has the USB vendor ID 0x1614 and product ID 0x0804. Communication with the device is done using the following endpoints:
dev->config.interface.altsetting.endpoint (endpoint 0x86 - input from the device)
dev->config.interface.altsetting.endpoint (endpoint 0x06 - output to the device)
I can probably work on creating a patch for usbobex.c if no-one else is interested in working on it, but I'll probably need some help if so.