Some of the current existing technologies are...
One of the Current Tactics developed and implemented in anti pirate boarding procedres is the fire hose. the crewman fires high pressure water at the assailant in hopes of knocking him off his rope/ladder.
Some merchant vessels put up segments of razor wire along the whole length of the ship making boarding nearly impossible without injury. The major problem with this tactic is its time consuming, unsafe for crew members and hinders pulling into port until it is removed..
There are defense personell that can be hired to guard merchant shipping. The downfall to this is they are not always 100% effective against pirate boarding depending on numbers, and they are fairly costly.