Open-source electronics platforms for rapid prototyping have already been around for a while, i can think of Arduino board but surely there are more of them.
The low cost, the wide variety of inputs/outputs, the ability to interact with sensors ot to control motors, the ease of use and the community, make these platforms a perfect fit for hobbyist’s and artist’s projects.
Regarding the ease of use, Arduino can be programmed in a c-like language ( additional straightforward libraries to access the board’s functions are provided ) and has a development environment based on the famous Processing.
And now, SUN Spot.

I’ve spotted the video embedded below on the googletechtalks youtube channel.

The platform developed by SUN Laboratories seems awesome:

Completely open source (hardware/software)

180 MHz 32 bit ARM920T core (with jazelle?) - 512K RAM/4M Flash

2.4 GHz IEEE 802.15.4 radio with integrated antenna

USB interface (host?)

2G/6G 3-axis accelerometer

Temperature sensor

Light sensor

8 tri-color LEDs

6 analog inputs

2 momentary switches

5 general purpose I/O pins and 4 high current output pins

100 mt max distance between Spots (more info on this on the sunspotworld.com forum, the devices together form a meshed network, so multiple stations can be used to extend the network civerage, but the maximum distance between two spots seems limited to that)

Missing agps and only 4mb flash you say? Looks like someone already built a custom gps module and SD module for their projects. Some new addons have been shown at JavaOne2008.

The SUN Spot can be programmed enterely in Java, and has a development platform based on NetBeans (Eclipse can also be used).
Refer to the embedded video for some example projects. Above all, watch @00:21 for the cool Sun Blackbox monitoring project.
It comes in a developer kit with 1 Spot base station and 2 standard Spots for under $700, a kit that reminds me of the early openmoko developers kit.
The two things that i found most intriguing are the ability to upload new “software packages” wirelessly (in this presentation is done through a management interface, could this be done dinamically using the java api provided?) and the way the meshed wireless network formed by Spots is managed (i should take a look at this sooner or later).
Additional videos about Sun Spot and projects based on it can be found on youtube.