Open Garden is a rather interesting app, that (sort of) implements Mesh Networking.
The title on Open Garden's website, doesn't give it enough credit.

"Share your mobile Internet among all your devices" -
sounds like basic tethering (connecting via your cellphone),
something that was already implemented on my old Sony Ericsson.

We are talking however, about a completely other level of "sharing".
If the idea is well implemented (which seemed to be on the Open Garden launch on March 4th),
It will let everyone share their network connection in order to benefit us all.

Say you have a better mobile reception than your friend, but he has to check
where you are heading to online, you can simply share you connection with him.
Connections can be chained, so people can connect through 4-5 different devices (and potentially more).

This has more implications, at a large scale this could potentially mean (if done securely of course), full connectivity within cities / large crowded areas.

Of course there are a few issues I could think of with the current module:

Security - it is discussed quite a lot on their website, the application makes you connect via VPN, so that should be pretty secured.
Inner-connectivity - I haven't seen an option for the devices to communicate (sms/call) among themselves, this is a critical aspect of Mesh networking IMO.
Why only Internet? - I understand that Internet connection is the most critical, and probably the easiest thing to share using Wi-Fi, but I also believe that
general mobile reception (for calls/sms) would also be a nice thing that you could share, this could be impossible though, which leads me to the next point..
Hardware - It is great that this could be done using Software only, but I imagine that it will always be "incomplete" and sort of unintuitive as long as the hardware
doesn't really support it out of the box.
Reach - this is perhaps the most important part, this application has to be installed on as many devices as possible, otherwise the entire idea is pointless, which
sort of explains why the website's title was more leaning for personal use - you can't promise that you'll always have someone near by that uses the app.

Another interesting app I've found that allows Inner-connectivity is the Serval Mesh Project.

The Serval Mesh Project is Open Source, and even though I can't seem to find
an option there to share an Internet connection, it is a really interesting project
that might complete some aspects that are missing on Open Garden.

All in all, it seems that Mesh Networking should really be a priority for Mobile Manufactures,
as it allows more movement for clients between Mobile Carriers.