What's a good upgrade alarm for my 2013 accord? I need that will sound on if bump or shock, impact. I would like to use my existing remote.

 

you will have to check with local shops if they can interface with the factory key fob. you may not be able to directly control an aftermarket alarm with the factory key fob. DEI/Viper is your best bet for aftermarket product.

the factory alarm is a closed system, meaning the receiver and all of the brains are inside the main computer along with a lot of other stuff. so all that you get from the unit are the various outputs for lights and horn and starter kill and the inputs are the door switches.

if you have an iPhone you could get a Viper startsmart and eliminate a keyfob and use your phone to lock/unlock/start/monitor/etc.