The NYPD is warning straphangers across the Bronx about a rise in theft on subways.

Police say thieves are targeting high end cell phones, such as the T-Mobile Sidekick, causing the spike. According to new NYPD data, there were 111 robberies in December ? a 59 percent increase over December 2007.

Officials are battling the rise in crime by assigning police officers on trains with bullhorns so they can give commuters safety lectures.

The Sidekick retails for about $300. The NYPD says other targeted phones include the BlackBerry Pearl.