I did a search on this and find alot of the info is at least 3 years old so what gps are you guys using for navigation that gives turn by turn? With the availablility of aux power, the short battery life of car gps units does not seem to be a problem. What I want to do is plot out the routes I want to go and hear turn by turn directions. Also want to have directions to local services like food, water, hotels, etc. so I'm leaning toward auto/car gps vs. bike specific gps.
Garmin Edge 705 does everything you mentioned except audible directions. It will beep when a turn is approaching, then again as you get close. The turn by turn directions are easy to follow. The maps include restaurants, hotels, hospitals, etc. What's not to like?
+1, the Garmin 705 rocks. The battery also lasts a long time too, about 10 hours when new. It pretty much does everything a car GPS will do except talk to you. It also does everything a regular cycle computer does.
As far as I know, ONLY car GPS units talk to you. They are impractical for cycling in a huge number of ways, so most likely you are out of luck on getting one that talks to you, unless there is something brand new out there.
I've been researching cycling GPS solutions as well (as much as a map page in a plastic cover and a compass largely satisfy my needs), and it sounds like the Garmin 705 is the be-all and end-all of cycling GPS options, but also a rather lousy product by comparison to other current GPS products, as far as map quality, resolution, detail and accuracy goes (though tell me I'm wrong if you've found otherwise, and I'll be delighted to hear it).
I'm happy with my Cateye, as far as cyclocomputer functions go, so that aspect of the device doesn't sell me. I'm thinking of just buying a Google Android Nexus One and going the Google Maps route, which adds no extra weight, since I carry my phone on long rides anyway. Not as convenient, but can't be beaten for accuracy (given that satellite images can be consulted for verification).
The garmin 705 is as good as it gets for a cycling GPS, but keep in mind, the lack of some functionalities are due to the need to make it really small, light, weatherproof, and have a nice long battery life. Added features have trade offs. I have known some mountain bikers and tourers to strap hiking/backpacking GPS units to their bikes because they want more of the topographic functionality and that seems to work pretty well too, you just have a weight/size trade off.