Bats activate tripwire, while it is intended* that they don't activate tripwire nor pressure plates, they are just for environmental and atmosphere reasons. Pressureplates is difficult to test, since bats always fly, unless they hang on the ceiling, but then the pressureplate has to be on top, which is not possible.
Evidence: https://www.youtube.com/watch?v=zyMvbA1s1cQ&t=2m05s

• http://minecraft.gamepedia.com/Bat#History see 12w42a