A Cateye Strada Wireless works well as long as your handlebar where you mount receiver/head unit is within X cm of transmiter on fork. X used to be about 70cm, don't know for certain now. I've used 3-4 generations of Cateye Wireless over >60,000 miles, they work well. Batteries (2, 1R+1T) in newer versions last over a year, unless you're riding in cold weather, then less.

I'm using this one now, because the display is larger/easier to read, it can be configured to display only the info you want, and it has a momentary backlight that you can see while night riding. Unless the manual has been revised, it is frustrating to set-up, takes a while till you figure it out, worse in this regard than any cyclocomputer I've used. Once set-up it's great.

If you want more, a smartphone with the right GPS nav app could be useful. Some apps allow you to download map databases and then it will provide real-time GPS navigation with only gps feed - no wifi or cell service or data plan required. Even a cheap tablet (with gps) will work - in fact these are better due to large screen.

Osmand is the best app I found when I looked a couple years ago. There are others too that I cannot presently recall. Osmand is free. It lets you download individual US states (vs entire USA), plus lets you store map files on external microsd memory (if phone/tablet has this capability) so the app+maps don't use all the device's built in memory. Has turn-by-turn voice prompting, available in several languages. The actual map files (also free) are not as fancy as some of the pay-apps' maps, lacking detail about nearby services, etc. Of course the one's you pay for may not be much better (or obsolete).

Here's a trick to extend device battery life: if you're in rural area and next way-point is >30 minutes away, use cyclocomputer to calculate when to turn device on, subtract a safety margin, turn device off and ride, then turn device back on at (X-safety margin) miles. Device will re-acquire satellites and resume gps navigation in about a minute, before you reach the waypoint. For example, if next waypoint is 5 miles away and you average 10 mph, and your present odometer reading is 1000 miles, turn device off until you reach 1004.5 miles, then turn it back on, leaving 0.5 miles/3 minutes before waypoint, which is plenty of time to restore gps navigation.

You can greatly extend device battery life and recharge intervals using some common sense and the power button. Naturally the device display consumes a lot of battery, but so does the gps radio, so best to shut it off (full power down unnecessary) when you have long runs to next waypoint where there's little point in having it on. This may seem a little convoluted but it's the difference between having to recharge 1-2 times a day and once every 3-5 days.