Laser tripwire security systems can be expensive propositions that don't always work as planned -- just ask Raytheon, which saw its $100 million Perimeter Intrusion Detection System for JFK International Airport undermined by one wayward jet skier. Taking that as a form of dare, Justin Huynh and teammates at Liquidware have devised a much cheaper (if also much smaller) tripwire of their own. Any interruption of a laser pointer's beam is caught by an Arduino light sensor that promptly sends the alert to an Android-running BeagleBoard xM; if a toy like Bruce the shark dares cross the line, the BeagleBoard sends a Twitter message to let the authorities, or at least Huynh, clamp down on the trespasser. The invention won't replace Raytheon's handiwork anytime soon, although Huynh notes that additional or more powerful sensors could theoretically catch real, muscle-bound sharks and not just their plastic counterparts. The supply checklist and source code are waiting on the company's project page below, so those who'd like to ward off miniature invasions can get started today.