Get a programmatical notification when an address receives a transaction I am experimenting building an in-house Bitcoin payment system. 

What is currently the recommended practice to get notifications to your web server when a certain Bitcoin address receives a transaction? E.g. trigger an action from somewhere which results a HTTP call made to a web server.

Are there any better alternatives than polling bitcoind? 

External systems (blockchain.info) are good to go too for me.

Any way to filter for certain confirmation threshold (e.g. need 6 confirmations)?
Polling bitcoind is superior to any other alternatives as there is zero lag, your operations don't depend on a 3rd party SPOF service, etc. 

A fresh incoming payment is also an outspent output, so calling bitcoin-cli listunspent 6 9999999 "[\"localAddressInQuestion\"]" will provide you with the exact unspent amount for this address only. Replace 6 with any number you wish to set as the confirmation threshold or make it 0 to get the unconfirmed payments as well.