I have a Garmin 64 and Garmin 62S, both work well for hiking, biking, driving, etc. The 64 series replaced the 62 series. I think there are three models in each series with a different variety of extras added in. My 64 will not work with a heart rate monitor strap, but the higher levels in the series I think will. My 62S does work with a heart rate monitor ANT+ chest strap.
Driving a long distance (hundreds of miles) they can choke on trying to find the best route. For routing, they have a driving option, a cycling option and a tour cycling option. Plus a few other options. I think that the tour cycling option will use bike paths where teh plain cycling option won't but I am not sure on that.
Uses AA batteries. Garmin sells a battery pack that if you are using that battery pack in the 64 series (but not teh older 62 series) the battery pack pushes down a button in the battery case that tells the unit that the rechargeable battery pack is in use. When that happens, you can operate the GPS on a mini (not micro) USB cord while you are also charging internal battery pack. And, if you are a bit tricky, you can put a little piece of plastic or metal over that button and put two NiMH AA batteries in it and it will charge the AA batteries that way. That is not something that Garmin wants you to know, they would rather have you use their proprietary battery pack.
I use Ikea Ladda rechargeable batteries in the Garmin 62S and 64, both have excellent battery life. But the older non-low-discharge type NiMH batteries have terrible battery life. Eneloop AA might also give good battery life, but I have not tried that.
I download maps and install them onto a micro SD card. The card does not come with it. Free maps available at:
http://garmin.opentopomap.org/ (you might have to click on the english flag in upper right corner to read it)
http://www.gpsfiledepot.com/maps/byuser/135/ (I do not think these are routable)
http://garmin.openstreetmap.nl/ (for a custom file that has map areas that you select, I use the cycling routable version)
https://www.openmapchest.org/ (I am not sure if I ever used these or not?, but I had the link on my computer)
http://www.openfietsmap.nl/downloads/europe (I think I put these on my Garmins but never used them)
In the GPS you select which map you want to have enabled and which ones to disable. So I load lots of maps onto the micro SD card, use the one that seems to work best for my purpose at that time.
In bright sunlight you can turn off the backlight to save battery power and see the screen well. You can't do that on a phone. I have them configured to turn off the screen after about 30 seconds or a minute to save batteries, touch a button and the screen comes alive.
The screen is not as hard as I would like. I got scratches on my Garmin 62S screen. When I bought my 64, I put clear packing tape on the screen (careful to avoid bubbles) to protect the screen before I ever used it. Have replaced the tape a few times.
There are similar Garmins that are more compact, not sure what the various models really are.
First photo, inside battery case on Garmin 64 I have a small piece of metal covered in black plastic tape over the button so I can use it to recharge AA NiMH batteries. If you do that and put Alkaline batteries in it and then plug in a USB cord, something bad will happen so never do that.
Second photo, Garmin 64 on my Sherpa. I have a DIY stem bolt bracket to hold it on the bike.
Third photo, side view of Garmin 64 on my Titanium bike using the Garmin handlebar mount. It is attached to handlebar with zip ties, note that I also have a small cord to keep it from falling completely off the bike if I do not get it firmly into the mount. The zip ties can break if your bike falls over and it hits something, carry spares on a bike tour.
Fourth photo, I am charging up a pair of AA batteries with a solar charger on a kayak trip last summer. In the photo I have an older GPS, disregard that one. I like that vintage GPS for canoeing and kayaking, but not for anything else.