is it possible to use an android phone to collect IMEIs or unique Phone IDs of phones within the same cell? Probably there is already some hack to use osmocom ... what I am looking for is an easy to work solution to scan traffic (by counting car drivers phones )
Well theoretically yes, but the problem here is that you need to know how the radio interface of your android phone works and have a driver for it before you can do that. As far as I know there are no such drivers for GNU Radio. The other problem is that the CPU on your mobile phone is not strong enough to handle the amount of data processing needed to perform such task, it may come a day when you have quad core CPUs with lots of RAM and strong DSP support, but I don't think we are there right now.