For a good deal of small mobile apps and simple web apps this would be a great tool for modeling simple CRUD workflows. I have several apps that this would be great for where 90% of it is just save and retrieve data where the other 10% need transforms or business logic, hence being able to place small transform scripts in the workflow. Now granted it's not going to scale to an enterprise solution, but there would be a lot of value to being able to stand a back-end up in a few hours by diagramming it out. I think of it as kind of like BPEL for REST services. If it existed I would pay for it, and I can't imagine that I am the only one.
I've signed up for iknode - it would be great to check it out!
In the case of iKnode, we are focusing mostly on web sites. I have to be honest. We don't particularly like the mobile environment so much, specially because it feels like a step backwards for standards. We believe firmly in the Web. So we do support mobile environments, but we are pushing for the web to be successful. Even if mobile is hot right now.
We are currently in beta testing right now. You might want to check it out:
* iKnode (http://iknode.com)
If you like an invite, just signup here: http://iknode.com/register/
If what iKnode offer doesn't match what you are looking for, don't dismiss the idea of a Backend as a Service just yet. Try the following as well:
* Parse (http://parse.com)
* Kinvey (http://kinvey.com)
* Stackmob (http://stackmob.com)
Among others...
EDIT: Fixed the Kinvey Link.