Kickstarter -- Arachnio

The Arachnio is an Arduino Micro variant with integrated WiFi via the ESP8266. It uses an ATmega32u4 as the main processor, so it's a drop in replacements for the Micro. As far as I know, it's the first Arduino variant with an ESP8266 on board.

That looks quite useful.

$25 for the early bird special seems a good deal. With shipping it comes to $50. If I can justify it, I'll give one a go.

Never used a 32u4 with the usb feature, the extra .5Kb of ram is nice.

What is more important I think is, can the ESP8266 be set into monitor mode?

It appears wifi dongles using the chip can, but whether it can be done from the AVR chip is a different story.

The international shipping is about as cheap as it gets with some rudimentary tracking and assurance that the package will reach the intended recipient.

The interface between the ESP8266 and the Atmega32u4 host is a straight TTL serial connection, so you should be able to do anything with the chip that the ESP firmware supports. You can of course update the firmware with a custom one that supports promiscuous mode or anything else the chip is physically capable of doing.

Seeing as the design files are locked until release, can you give insight as to whether I would be able to use a 16Mhz crystal.

It appears that the board must have an external 8Mhz connected to the XTAL pins? Is there a reason for not using 16Mhz. I guess power savings, just seems like it could be quite slow for any substantial amount of data transmission.

The reason it's only 8 MHz is so the 32u4 and the ESP8266 can be run off a common 3.3V rail or a single LiPo cell. Now, it's possible to overclock the 32u4 such that it's running at 16 MHz by swapping the resonator for a 16 MHz, but be aware that it's not spec'd to run at 16 MHz at lower voltages. Just make sure you use a resonator that's accurate enough for USB.