At least in Argentina (not sure about other Spanish-speaking countries) "handy" is used for walkie-talkies, but not cell phones. I wonder if it comes from the German use of that word, or if both languages borrowed it from somewhere else.

Checking the Wikipedia article for walkie-talkie just now, it seems the formal name for it is "handheld transceiver", so it makes sense that "handy" would derive from that.

Edit: I was too lazy, scrolling down a bit on the same article mentions and explains the term "hand[y|ie]".