The EOS M is a compact interchangeable-lens (mirrorless) camera from Canon due to be released in October. It's actually a Rebel T4i in a much, much smaller body that weighs much less. It might be (but I'm not 100% sure about this) the smallest compact interchangeable-lens camera with an APS-C sized sensor.
What's good about this camera is that it is very small and weighs very little, which means it will be much more fun to carry around than a DSLR. It packs a big punch with an 18 megapixel APS-C sized sensor. While it won't quite match the image quality of the Fuji X-Pro1, the Sony NEX-7 (although Canon lenses are better than Sony's lenses) or the Samsung NX200, it is better for video than those three cameras.
If you're planning to use a camera more for video and less for photographs, then the EOS M is the camera for you (or the T4i if you want a larger camera). It's also smaller than the three cameras mentioned above, so that might also be a reason to choose it.
The EOS M has its own type of lens mount, which means if you own a Canon DSLR, your other Canon lenses won't work with this camera (although I'm sure an adaptor will be available at some point). Canon announced just two lenses for this camera, so pickings are slim.
The MSRP for the Canon EOS M is listed at $800 with a lens, which is a fairly reasonable price. However, the NX200 and Pentax K-01 both have an MSRP of $900, but you can get them for as low as $750 (with a lens) if you shop around. The Sony NEX-5n, which has an MSRP of $700, is another good alternative . If you're not going to use the camera much for video, those might be better (and slightly cheaper) choices.
The bottom line is that if you're in the market for a small and light-weight digital camera that packs a DSLR punch and is great for video, while at the same time doesn't break the bank, the Canon EOS M is for you. If you are primarily interested in a camera for photography and not video, there are good alternatives to consider.