One of the great strengths of LightweightM2M (LwM2M) is to be… ahem… lightweight! The fact that it relies on CoAP for the communication, and that all the standard resources are meant to be very concise really helps making very small implementations that can fit in constrained devices.
In the video below, you can see how Eclipse Wakaama (a C implementation of LwM2M) has been ported to an mbed NXP LPC1768 – a device with just 32KB of RAM! – and is controlled from Eclipse Leshan, a LwM2M server in Java.
What I really like in this video is that it shows how simple yet powerful LwM2M actually is, and how efficiently you can fit advanced features like firmware upgrade in very constrained devices.