That app was on a very old lg mobile phone before iPhones I never used it to harm people I showed them the app so they new that people could do that sort of stuff and that allowed camera controll, calls listen to you call, make a call myself and use your credit, sms texts , email, core to copy of your phone contacts and messages to my phone , a lot more that I can't remember and like I say that was 5 years ago.
I imagine if I wanted to do that now wifi would be better than Bluetooth and most people if any that are trying to hack your phone would use a wifi connection
1) there are more people that leave there wifi on and connect to insecure networks allowing for more targets and minimal tools just a laptop and software.
2) wifi is faster than Bluetooth allowing me to copy more of you data in the moment that I have got access to your data
3) wifi has more protocols
Essentially everything can be hacked by any one who has got the tools and the knowledge but it's normally your own stupidity that gets you hacked eg weak passwords and connecting to insecure networks with wifi is a huge risk you don't no who else is on the network and what they are doing
I would say bluetooths pretty safe these days as wifi attacks would be a better approach and I would have be in a 10 meter distance of you at all times or the connection would be lost so I would be pretty much drivng at the side of you all the way to your destination