Very early on in my career I had the privilege of working with a manager who shared your father's philosophy. The experience left a lasting impression with me, and has led me to seriously consider whether management is something I'd be good at or would even want to do.
Perhaps most enlightening was her stance on promotion. Our department had been, overall, falling seriously behind and, as a result, the other managers hadn't promoted anyone in many years(!). She and I discussed this one day and, to paraphrase her words, she said: "At the end of each year, there should always be someone ready for the next level or getting close. If there isn't then I haven't done my job; I haven't appropriately challenged them. My goal is the growth of my reports, and their success is mine."
The creator acknowledged this possibility [1] (fwiw it appears they do use accelerometer data to discount obvious false hits), but mentioned that they hope to include a proximity detection circuit in the multiplayer adapter so that scoring will be more honest.
My thanks to you and your team for having developed this. The cost of crypto is, at present, far too high for mainstream use - or so it seems. Undoubtedly, the challenges inherent with its correct implementation are a part of the reason for that high cost, but the media's depiction of the field is certainly no help either.
How technical is your audience? It's been posed elsewhere in these comments, but one area that I'm particularly interested in is your proposal for key exchange. For example, your site warns the user to never email or IM their password: that's great advice, but I don't see any suggestion of a suitable alternative. Granted, I would consider your primary audience to be proxy: that is, the recipients of encrypted messages compelled to install your extension on their machine. Your take may be different, and of course these individuals may simply use-it-and-forget-it, but I'm sure that some of them would want to become your users as well. In those cases, the copy for this section may be confusing or thought incomplete.
What happens to my plaintext once its recipient has decrypted it? From the source, after passing the encrypted data to sjcl, it looks as though the plaintext is simply appended to the DOM in place of the encrypted message. Are we certain that Google is not performing any kind of DOM analysis? I don't know how Google behaves in this regard; what assurances do I have that my decrypted messages are still secure?
With a lack of deeper technical details regarding your implementation (understandable considering your proposed audience), should I assume that you're using the sjcl default of 128 bit AES in CCM mode? Would you consider publishing these details on your website? My apologies if I've overlooked them.
I'd like to echo IgorPartola's sentiments and upvote, however little that may be worth. Usability is crypto's silver bullet and any reasoned discussion which furthers our attention to this problem certainly has value in my opinion.
Perhaps most enlightening was her stance on promotion. Our department had been, overall, falling seriously behind and, as a result, the other managers hadn't promoted anyone in many years(!). She and I discussed this one day and, to paraphrase her words, she said: "At the end of each year, there should always be someone ready for the next level or getting close. If there isn't then I haven't done my job; I haven't appropriately challenged them. My goal is the growth of my reports, and their success is mine."