Along the same line with the New Testament use of the Old Interactive tool, I'd like to suggest an interactive tool that deals with how the Apostels (Acts - Rev) use, allude etc. what Christ taught in the gospels. I don't think anybody has come up with such data yet. But the New Treasury of Scripture Knowledge would be one resource to consult for that. I was also thinking of some NT commentaries like some of the Hermeneia Series that have a section that deals with Sayings of Jesus etc. as part of the authorship discussion. There might be other resources that can be consulted and others could help suggest them.
I find it interesting that we have scripture harmonies of all kinds but none that deals with how the teaching of Christ was used and interpreted in the apostolic writings. I love to explore how e.g. the law was interpreted in the historical and prophetic writings, then how the OT was used in the NT. For me the next step would be to trace how the apostles have used the teaching of Christ in their writings.