iPhone Contact List - Custom Labels recognized as a Mobile Number When a number is labeled as "mobile" in your contact list, you can click the little "cloud" shortcut to send a text message to that number.

If the number is labeled as "Home" or anything else, that text message short cut goes away (because the system thinks it is not a mobile number)

My question is, can you use a custom label and somehow tell the system that the number is a mobile number so you can send text messages to it?

I have a lot of contacts that have more than 1 cell phone and it would be nice to be able to label them as something other than "mobile" so that I know which cell phone i'm texting.

Having all the numbers labeled "mobile" does nothing to let me know which number is which.
If you set it first set it to Mobile or iPhone, then select Add Custom Label, it should treat the device as a mobile device (since that was the last "non-custom" label selected).