This looks good - I'm always happy when I see tools that allow offline operation and integration with open standards for data formats/sync protocols.

This, gollum style wikis, bugs everywhere issue tracker, etc can make a great working environment that provides offline capability without vendor lock-in to a saas platform

Yes, tools which support open standards are dwindling. One of the few well-maintained iOS/Android/Mac todo apps which supports CalDav is 2Do, http://www.2doapp.com.

It's sad how Google, Apple et al. have mostly abandoned the use of open standards in favor of locking users to their own closed, craptastic, proprietary services. Lack of interoperability severely limits the usability of cloud based services. Sadly these vendors seem unable to produce decent tools that work well together, so users are left with their data scattered across crappy services (e.g. Google Apps/Drive/Docs/Calendar etc.).

Lack of interoperability, vendor lock-in, poor usability of many web based apps and crappy touch based UIs makes me feel like we are living in the dark ages of the information society. It's almost as if people have forgotten how powerful tools we had 20 years ago compared to the current web app bloatware and how efficient keyboard + mouse is compared to most touch based UIs.

I have no love for Google, but I'm not sure how you somehow group "touch based UIs" into "proprietary services".

There are plenty of great apps on mobile devices that support open standards. The whole point of an open standard is that you have the freedom to choose how you consume the data - be it a terminal/shell client, a desktop GUI client, a mobile 'touch' client, a web client, whatever.