Swim Harness/Tether

I just got a small above ground pool for my kids in the back yard and want to get some sort of inexpensive swim in place system so that I can get some good swim practice out of it for myself.  I was wondering if any of you have had any experience with the following systems and if so if you would share your comments (pros and cons) on them, or if there are other good systems you have tried that I do not have listed below. 

Thanks,

Lisa

Riptide http://www.swimriptide.com/

Proswim  http://proswiminc.com/

API http://www.api2000.biz/

Aquacise http://www.swim-in-place.com/

Active Forever http://www.activeforever.com/p-1343-home-swimmer-portable-stationary-swimming-system.aspx?source=overture&OVRAW=Home%20Swimmer%20Portable%20Stationary%20Swimming%20System&OVKEY=home%20swimmer%20system&OVMTC=advanced&OVADID=32643996511&OVKWID=236438507511