The Global tops, since they do 5hz natively including the HUD model:

http://www.buygpsnow.com/search.aspx?keyword=globaltop

the new iTrek coming out does too, and may have a better bluetooth handling (when you disconnect, the GTs turn off after a while except for the HUD model - the iTrek will go to sleep and power up when the BT link is reestablished according to their blurb).