I think you might be mistaken on the last point about app compatibility in your earlier post. From what I understand, the change from Dalvik to ART is only a change in the runtime, not in the .apk files that the applications are written in. That is to say, developers won't be forced to rewrite their software for the newest system except to take other new features (such as UI changes) into account, but that's no different from any other android release.
The article says, "Google partner with three Indian OEMs to create a Smartphone with dual SIM cards, an SD card, 4.5 inch screen, and FM radio for under $100.", but on the contrary there are not even a single OEM in India manufacturing their own mobile handset, then from where Google has found three different OEMs in India?
With this announcement, the spread of Android will be expanded across the electronic devices, but the major problem with Android is its updates for the future releases. None of the Android releases in past are compatible with the existing old hardware. If this continues then this will be simple increasing the electronic waste in multiple folds. As if you change only the single device you will have to throw all of your other devices connected with it. Although it is committed that, "The software on Android One is the same that runs on stock Android. It allows audience and installers to install relevant apps and provides full automatic updates.", but this will be having many catches.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.