Generally on Android, if you simply display the phone number, and the user taps on it, it will pull it up in the dialer. So, you could simply do
For more information, call us at <b>416-555-1234</b>
When the user taps on the bold part, since it's formatted like a phone number, the dialer will pop up, and show 4165551234
in the phone number field. The user then just has to hit the call button.
You might be able to do
For more information, call us at <a href='tel:416-555-1234'>416-555-1234</a>
to cover both devices, but I'm not sure how well this would work. I'll give it a try shortly and let you know.
EDIT: I just gave this a try on my HTC Magic running a rooted Rogers 1.5 with SenseUI:
For more information, call us at <a href='tel:416-555-1234'>416-555-1234</a><br />
<br />
Call at <a href='tel:416-555-1234'>our number</a>
<br />
<br />
<a href='416-555-1234'>Blah</a>
<br />
<br />
For more info, call <b>416-555-1234</b>
The first one, surrounding with the link and printing the phone number, worked perfectly. Pulled up the dialer with the hyphens and all. The second, saying our number
with the link, worked exactly the same. This means that using <a href='tel:xxx-xxx-xxxx'>
should work across the board, but I wouldn't suggest taking my one test as conclusive.
Linking straight to the number did the expected: Tried to pull up the nonexistent file from the server.
The last one did as I mentioned above, and pulled up the dialer, but without the nice formatting hyphens.