After the last draft released in december, the COAP folks just released a few days ago a more refined version of the COAP draft, with additional thoughts on coap-http mapping, RESTful verbs for constrained environments, and pub/sub notifications, and more.
This document specifies the Constrained Application Protocol (CoAP), a specialized RESTful transfer protocol for use with constrained networks and nodes for machine-to-machine applications such as smart energy and building automation. These constrained nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while networks such as 6LoWPAN often have high packet error rates and a typical throughput of 10s of kbit/s. CoAP provides the REST Method/ Response interaction model between application end-points, supports built-in resource discovery, and includes key web concepts such as URIs and content-types. CoAP easily translates to HTTP for integration with the web while meeting specialized requirements such as multicast support, very low overhead and simplicity for constrained environments.
Definitely worth looking at it and try to reuse as much as possible from there in your designs. I’ll be analyzing it soon and give my thoughts on it later.