Android 4.0+: Check out BarSense – a simple bar path tracking app.

Useful not just for weightlifting, but also for squats (see examples here) and all your other favorite lifts. The developer is taking your feedback in this reddit thread.

Richie Patterson said:

Great app, used it on all my lifters tonight, gave them some quick/instant feedback on their lifts.

Price: Free!

Download: BarSense on Google Play

Features:

paint bar path

calculate bar velocity

Premium Features: 1.49 Euros in App Purchase give you

force graph (in Newtons)

power graph (in Watts)

distance graph (in Meters)

How to: 1. Record/ choose a video. 2. Focus the plate. 3. Get Bar path.

Video Instruction

Alternatives: