In another implementation, the second mobile device could also optionally present {HEAD ~ a distance} to {TAIL ~ the first mobile device} 
In another implementation , the second mobile device could also optionally present { HEAD ~ a distance } to { TAIL ~ the first mobile device }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL