I've got one of those electrical impedence bodyfat testers, and it seems to be consistent to +/- 0.5% I don't know if it is bang on accurate compared with other measurement methods, but its been quite usefull for tracking my cutting progress. The only thing that presents a problem is my hydration levels. I.E. if I'm dehydrated the readings are way off.

Since you retain some water on many types of gear, wouldn't this effect the measurements? How do you guys keep track of BF while on gear? I imagine skinfolds wouldn't be accurate if your bloated either? I know that weight loss is not normally an issue on gear, but if I'm planning on drastically increasing my calorie intake for 8-12 weeks, I want to make sure that the weight I'm gaining isn't too much fat with the muscle (and water).