Jefit is a great app. I used it for a while and then switched to another. I just re-downloaded it after reading this post. It looks like it’s been updated since I first used it. I’ll be interested to see how it works.
I’m currently using GymGoal. It’s a great app, but currently only available for iPhone/iPad. It was the most flexible app I could find, allowing for custom exercises and different set combinations. The newest update allows for 4 different workout sessions on the same day. Setting up your routine takes some time, but once it’s loaded, when you get to the gym, it tells you which routine you’ve scheduled for that day. You start logging and it takes you through the exercises, including timed rest periods. You can add extra sets quickly and delete sets or skip exercises if necessary. At the end, it will e-mail you a summary of your workout, and everything is backed-up to their server. Best of all, it’s free. There’s a paid version with no ads and better formatting, but the free version is great.