Sorry for my late replay, I was busy with my SAP Teched sessions, Bangalore.
Coming to the point on custom app development using Syclo, SAP itself is not recommending the approach of doing so, the answer for this you can find from Syclo product team itself 
(hope http://scn.sap.com/people/wim.verhelst can give more information on this).
When we say custom apps, the SAP recommended approaches are to go with go with SMP - Odata native or Hybrid or web, based on the business requirement.
- Midhun VP