Thanks for your replies. The LCD will be fixed near the parking lot (and the Arduino), and I don't think it's a problem if a random driver can read it, actually part of the plan is the LCD to let the unauthorized driver know that he/she cannot park there, at the same time letting know an authorized driver that he can do so. Security issues (stealing it etc) won't be a problem either. Regarding the position of the car, mostly it'll be with the front. But now that you mention it, maybe I should put some sound alert based on the situation.
So you think I should go ahead and buy the exact modules I listed above? Reading around I haven't been able to confirm that all this will work with commercial ibeacons, some people refer success with an ibeacon based on the HM-10 module, but no one with commercial ones (like the one I mention above). Another issue I'm not sure about is if the Android smartphone will needed to be paired beforehand via bluetooth with Arduino or it can work without doing so? Thank you for any input on my project, I'm new to all these, I'm searching around, but sometimes things are not clear to me, especially since I don't own an Arduino atm.