So, a few answers:
Yes, you can do encrypted mesh networks over long range. I'm a hardcore robotics guy at heart - the name "Flutter" was chosen exactly because this protocol is designed to be as lightweight as possible, and though the mesh protocol itself is still being developed (basically, that's why we need kickstarter, aside from the fact that I'm tired of ramen), I really intend for the protocol to stay out of the way. You'll also have full control over what happens, so you can always turn meshing off and use hard addressing. It's still really simple to use that way and cheaper than everything else I've seen that compares.
I absolutely will not sell a product as "cryptographically secure" unless I believe it is, and I understand that the "smallest" flaw in a cryptographic system can render the entire system worthless. I am learning everything I can about cryptography, starting with some amazing e-books I have found on the subject, and just like wireless
Our data rate is proportional to our range (this is generally true for any radio system), so we get 1km range at low data rates (1200baud tested, but we physically ran out of test room and had a strong signal). Theoretically this radio can do 3km at 1200 baud and it looks like we should be able to do 1km at 30kbps at least. Also I think the new radio chip doubles all the data rates in these cases (I would have to confirm), and I do know the new chip has higher transmit power and higher sensitivity, so range should be even better.
There is a cheap radio amplifier (PA and LNA) called the CC1190, and texas instruments has all kinds of datasheets on using either of the two radios we are working with to give us 10km range, or much better data rates at 1km, etc. We're going to design the protocol with expansion in that direction in mind, if people really dig the range thing (it's a bit much for a beer brew setup, but if you want dark meshnets, lets do it!)
I'm a hacker at heart. I first learned lockpicking at the old Noisebridge location (the original one). I love 3D printers and open source, did a rant/thread about open hardware on the Ultimaker mailing list a year back (I was one of the first in the bay area to get an Ultimaker too, and designed a new mount for it that I have on thingiverse). I got on hackaday for some 3d printed helicopter blades, and have been building robots since I was 15. There's a longer bio about me on our site, at flutterwireless.com
See also me ten years ago talking about robots (and I feel silly for the "few people do" comment, but I was 15 and trying to keep it simple). http://www.youtube.com/watch?v=8FJu1eL_dYs
Please ask me anything!