Your experience using fetal dopplers?

i rented one from babybeat. it worked great. i found the heartbeat everytime. it depends on what kind and how far along u are. the ones from walmart dont even work at 28 weeks so i wouldnt get that one. it was differnent places where i would find my babys heartbeat becausee he grew and was always moving. i sent mine back when he started moving all the time.