several here   https://www.google.com/search?source=hp&ei=RQtFW56lHYi6tQX0gY-gAw&q=iPhone+app+for+marking+two+points+and+creating+a+gps+line+between+them&oq=iPhone+app+for+marking+two+points+and+creating+a+gps+line+between+them&gs_l=psy-ab.3...778344.778344.0.780826.4.1.0.0.0.0.400.400.4-1.1.0....0...1c.1.64.psy-ab..3.0.0.0...0.kyyB8ROF608

Got a new computer and it sure doesn't want to make link.