I've tried a couple, and neither one worked on my Motorola phone:

Bike Speedometer - it was off by about 5 mph which made it useless
Move! Bike Computer - seemed to get the speed correct but it was only flashing a readout about once every 30 seconds. Not very useful.

CycleDroid - I'm about to try it today - hopefully this one will be better. If not, I've seen a lot of positive reviews of IPBike, although many people complain that it's interface is too cluttered.

If you have any suggestions, please let me know. Thanks.

I've tried Android-Speedometer, to simply display speed in a large widget. It's fairly accurate.

The problem is there is a lag when your speed changes and the display, because these apps have to average several readings. The GPS sampling rate is much slower than it is with the switch on the wheel, and they also tend to cut the corner in calculating the speed, so it's often slower than the actual speed of the bike. It's just about unavoidable with these apps.

Endomondo ... been using it for years.

Those both look nice - especially Endomondo where you can get a whole training regimen on your phone. CycleDroid worked great for me today in terms of just a basic speedometer and a few simple computer functions, but I might have to give Endomondo a try.

I think the training stuff on Endomondo is for premium members only (there's a monthly fee for that).

I just use the free version. I use it to track my commute miles, as well as my recreational miles. My heart rate monitor syncs with it, so I can watch that and it syncs with myfitnesspal which I use to tack calories in/out.

My only quibble with it is there is no setting in the app to keep the screen on constantly when I'm using it.

You should be able to go into your display settings for the phone and turn off the display time-out setting, or put it on a very long period before the display shuts down, like 30 or 45 minutes. But, you've probably already figured that out. I can see how that would be a hassle. CycleDroid stays on all the time, but I doubt it would plug into your other fitness monitor devices.

I've tried ... for some reason I can't set it like that. The longest I can set it for is 10 minutes.

I use "Power Toggles" which allows you to put system settings (among other things) into a button bar widget. One of the available toggles is never-dim on the screen. It stays on until you toggle it off. Worth a try.

Yup, I used the same on my last Android phone - worked great. The new one has the latest Kitkat version of Android and already has that as a settings option.

I tried a few of these apps, but there are so many limitations like battery life, screen brightness, how to mount on your handlebar, apps crashing when you get a phone call or try to take a photo. I finally gave up and bought a Garmin, which solved all my problems.

The new Garmin Touring with maps and navigation is only $250 complete.

Since I already have my phone holder mounted on the handlebar and my Google Maps on Android is a better GPS system than my Garmin, I was looking to add some speedometer functionality to the phone. But if it doesn't work, I'm willing to find a place to mount the Garmin. On my old phone, I had the battery problems with GPS you are referring to, but this new phone seems to have much better battery life and efficiency.

My phone holder is actually the belt-clip holder from my phone's Otterbox Defender protective case - I zip-tied it onto the handlebar and it works perfectly:

"OsmAnd" for android works fine without needing a data plan, uses gps data for navigation,

What do you do when it rains? I prefer to keep my expensive phone tucked away safely in a waterproof bag and use a cheap(er) Garmin device for this stuff.

I have used Endomondo in the past, however, and it worked pretty well but drained the battery in about two hours even with the screen turned off. I assume things have improved since then.

When it rains I stick the phone in my raincoat pocket or a rain proof bag in my backpack. The phone claims to be "splash proof", but I'm not going to test it. I lost my Blackberry a few years ago to a 2-second bathtub dunking.

I have a handlebar mount that has a window in it ... so far it's worked fine in light rain, but it was cheap so I'm not expecting it to be totally waterproof. In the event of heavy rain I just start endo and put it in my backpack or my rain jacket

I have been using the free version of Endomondo for a long time and recently added a Garmin GSC-10 speed/cadence sensor to it on my Samsung S4 (native support for ANT+). Endomondo reads it fine, does not get interrupted with calls, emails, music changes, etc. I use a Quadlock case and bike mount. Tracks PR's, distance, speed, HR if you have a monitor, cadence with a sensor, calories (questionable as they all are), mapping via GPS, has routing planning on the free one even. Free does not support the training feature though.