I have two of those toys on my desk right now, they are useful dev kits for the TI CC1110 microcontroller - an 8051 based core with 32K flash and 4K RAM.
You also get a CC1111 part inside the wireless dongle which comes with it.
If you look at the PCB in the device, it is a hardware hackers dream. The debug port is broken out onto pads inside the battery compartment, and there are test pads all over.
The SPI screen is bitmap addressable and the keyboard is sanely wired up. You even get a piezo buzzer and 2 LEDs under software control.
It also runs at 2.5V on 3 AA cells, via a pretty nice LDO regulator that cuts out at 2.9V, so a set of NiMH cells will run down to 1V per cell, squeezing out almost every last drop of juice.
One of my IM-MEs cost Â£1, I forget what I paid for the other one, but it wasn't over a fiver.