Check this out, looks pretty cool! Ill wait for the prices to drop though, hope they work well and stay on the market.
http://cgi.ebay.com/HYDROMETER-Hand...emQQptZLH_DefaultDomain_0?hash=item359c033dcd
http://cgi.ebay.com/HYDROMETER-Hand...emQQptZLH_DefaultDomain_0?hash=item359c033dcd