If you go the caliper route, it is better to have someone do it who knows how to do it and has done it thousands of times. It is not recommended to do it yourself.
Bioelectrical Impedence is actually fairly accurate, especially when compared to calipers. Just make sure that you are hydrated and have stayed away from sodium in the past 24 hours It may be better to invest in a hand-held one, rather than a scale.
If you can, try to find a college/university near who does the bod-pod or hydrostatic weighing. It will cost you nothing and is the most accurate, while you are alive. 