Are recent affordable EEG devices any good? I'm looking to do some research about flow and optimal experience with EEG. 
I don't have access to a lab and I was wondering if the new devices that are available to the public (i.e. Melon, Muse, iFocust,...) are any good to conduct research? Is it all just a marketing gimmick?
The Emotiv system has been evaluated in a research setting. Badcock et al. (2013) recorded EEG activity with the Emotiv EPOC and a more conventional laboratory system simultaneously, and found that both systems produced similar results for ERPs with a relatively high signal-to-noise ratio, but it was harder to detect less reliable signals with the EPOC than with the standard lab setup they used.

Reference:

Badcock, N. A., Mousikou, P., Mahajan, Y., de Lissa, P., Thie, J., &amp; McArthur, G. (2013). Validation of the Emotiv EPOC® EEG gaming system for measuring research quality auditory ERPs. PeerJ, 1, e38. fulltext