I'm not aware of any, but I haven't looked thoroughly for one. There is a dearth of such software in linux generally. The only ones I know (e.g., OpenFitness by workoutware.com, which you must purchase) are for the desktop. You might be able to port it to your tablet, although I suspect you'll have problems w/ the gui interface even if you could get it running. I also don't think it is open source, which will limit tinkering.

Another route to consider is if you can get the Palm Garnet emulator working well enough on your system, is to run one of the many PalmOS diet & fitness apps. Again, these tend to not be free, but some might have trial period that would allow you to experiment to see if you can get it running well enough to use.

I've just tended to use a spreadsheet for logging my workouts. I tried several types of dedicated programs, but always found them not flexible enough for my needs. For instance, I will do different types of cardio workouts, and like to see how I'm doing in like types of workouts. I can put my rowing erg on different sheets than my NordicTrack or outdoor workouts, and further divide them into interval days and endurance days. I can then easily pull the data together by week & month, as well as easily compare how I'm doing for each type of work out. I can then develop charts and graphs to look at almost any aspect of my workouts that I want. You can do the same types of thing for strength training, although, I've found a cheap notebook the best, with some summary stuff on the spreadsheet. If you go this route, you can use gnumeric on your tablet.

I hope that helps, even if it isn't the answer you were probably wanting to hear.