yes something like https://kvdb.io/ or https://github.com/jgarzik/kvapp would work, just use PUT to save data and GET to retrieve it. But as you said, far from ideal if you just want to share data on the same device
Good news. We just released a service that enables communication between apps. You can learn more at https://dacrosse.com
Every person is considered a user (so that means developers and end consumers of CIQ apps). Each installation of a CIQ app using the service has a user id that is registered to allow access to the communication service. A user can have multiple devices, and multiple apps, all using the same user ID and all able to theoretically communicate with each other (if the apps are programmed to do so). Access can be renewed every 120 days (for now). We can add recurring subscription or longer terms easily if there is enough interest.