I had the Viper 5701 installed last summer. I did not get any additional options and had them not connect the siren. My only gripe with the system would be that the buttons on the remote are easily pressed while in your pocket. Also, being a butterfingers, I constantly was dropping my keys and breaking remotes. I have gone through 4 so far.
Just last month I had the iPhone module installed. This allows me to not have to carry any remote any longer. I leave the two way in my bedroom so that if the alarm goes off, I can hear the noise from the remote. I also keep the 1-way spare remote in the locked glove box "secret compartment" just in case there is no phone signal in the area and I have to disarm before starting. Now i can start the truck in the morning with my phone, unlock it with the phone when I am heading out the door, lock it when i get to work with the switch on the inside of the door, and arm the system when I'm at my desk. I love not having that remote in my pocket anymore.
Your experience may differ having the newer remote which I would hope has been improved. The iphone app is two-way in the sense that it will confirm that actions have been completed (such as confirming that your car has received the signal). However, it does not distinguish between a remote start or a remote stop and it will not alert you when your alarm is going off. However your existing remote will still alert. They are still working on the app and this may change over time.