These are reasonably cheap Arm processor boards with a lot of peripherals and IO built in. The FRDM has a 3 axis accelerometer for instance and only costs $9 – which is amazing. Additionally the FRDM can have a software change to make the board mbed compatible. mbed is an online compiler with an API for embedded ARM based controllers that is provides the same API across a range of boards.
After using the mbed system for a short time I have become a fan, the benefits of being able to just drag the compiled code to a mounted drive, to have integrated version control, a simple consistent API across the different features of the board, many user written libraries easily dragged into the project along with printf based debugging through a USB hosted COM ports out weighs the lack of a true debugger.
It is possible to easily manipulate the hardware including using interupts, timers, accelerometer and even I2C for example without really need to worry in detail about an bit manipulation of the Arm registers. It is not that difficult to figure out the bits but it is confusing an error prone and gets in the way of thinking about the code.
I am able by comparison to get work done using the Blueboard and the Open source CooCox compiler (which allows me to debug using the JTAG board).
However the CMSIS libraries provided for Arm libraries are not quite at the level of ease of use of the mbed stuff (partly due to the lack of documentation as there are things I keep finding).
One of my main goals for these boards is to make toys – I have ordered various sensors of ebay and along with the on board accelerometers I think I can produce something intriguing. Well I hope so.