Hey b4a!
Have you looked at the Arweave Zapier integration? It offers events for new transactions (which you can then filter based on tags, etc), and the ability to create and sign new TXs. It was a hackathon project, so it is still kind of rough around the edges.
Some details/demos here:
https://medium.com/@arweave/build-permaweb-apps-without-code-3-arweave-zapier-tools-you-can-make-in-less-than-5-minutes-e1837f1d3fea?source=---------27------------------
What _really_ sucks about it is that Zapier is totally closed source, and fairly expensive, too. Better solutions welcome!
-arweave-sam