I would use Java OSGi to read the JCR and show the data result result in an AEM page (or component). You can use OOTB form component as a starting point.
You can write an OSGi Java service that can read (ie - register details from JCR ) and write data to the AEM JCR. See this communtiy article as an example:
Querying Adobe Experience Manager Data using the JCR API