6LoWPAN module with IPsec on 868 / 915 MHz for your application.
Why I wrote the IoT M2M Cookbook
In my more than 20 years working with a manufacturer and in distribution I gave the same hints and recommendations to developers of wireless applications again and again. In May 2012 I made the decision to write the story that I have to tell weekly to customers in a book. The target is to guideline developers from the idea for an IoT / M2M device to a final product with mass production.