Merge (append) GAE datastores from different apps
You can use UrlFetch in App2 to request all the data you need from App1 and proces it to create your merged result. It is quite easy to serve and serialize the entities (with a cursor) using JSON for the data exchange in App1.
I have 2 different apps that are basically identical but I had to setup a 2nd app because of GAE billing issues.
I want to merge the datastore data from the 1st app with the 2nd apps data store. By merge, I simply want to append the 2 data stores. To help w/visualise
App1:

SomeModel
AnotherModel

App2:

SomeModel 
Another Model

I want app 2's datastore to be the sum of app2 and app1. The only way I see to transfer data from one app to another on the app engine administration page will overwrite the target destination data... I don't want to overwrite. thx for any help