BlackBerry PlayBook let you simulate real law enforcement lights with optional siren sounds. You can select from USA or European police light and siren, with 5 different siren sounds that you can select from. You can also simulate Emergency lights with siren sound and set the light sequence to imitate Standard or Cruiser cars. Purchase this app for only $0.99 in BlackBerry App World.
Disclaimer: The purpose of the Police Lights app is purely for entertainment use only. Do not try to impersonate the Police. It is against the law.