In the last years Mobile Brain/Body Imaging (MoBI) has been increasingly used to study cognition in the real world to give more ecological validity to brain imaging studies currently carried out only inside the lab. To increase portability of the setup and reduce cabling it is possible to perform a unified and real-time synchronized recording of data from multiple sources. However, delays and jitter may impair the quality of the subsequent event-related potential (ERP) analyses. Here we used an online auditory oddball P300 paradigm on one subject to compare the quality of P300 ERPs obtained (i) with online synchronization and alignment and (ii) offline with conventional alignment (synchronization channel) while sitting. We showed that offline and online synchronization strategies provided comparable although slightly different P300 ERP. We also recorded the electroencephalogram (EEG) while walking indoors and outdoors. A decreasing P300 amplitude respectively from sitting to walking indoors and outdoors confirms the dual-task effect on P300. These results show that integrated real-time P300 protocols are feasible but it is also necessary to test delays and quantify the jitter among different signals when developing real-world MoBI applications.