An obstacle alert device is capable of indicating clearly presence of an obstacle approaching a vehicle to a driver, without impairing visibility of a peripheral situation of the vehicle. Also disclosed is a system, method, and computer executable code for collecting, forwarding, and analyzing cardiovascular sound signals, where the collecting and analyzing may occur at locations that are remote from each other. The particles can be used to identify and quantify analytes in an analytical sample by reaction of the analytical sample with the particles.