The result left Cameroon, who have two matches to play, facing the possibility of missing out on next year's finals after a run of eight successive appearances.
Eto'o, the African Footballer of the Year, hit the bar with his 87th-minute spot kick.
Senegal, who top the table with 10 points from four matches, had coach Amara Traore sent off for protesting while goalkeeper Bouna Coulibaly made a string of fine saves before going off injured.
