Geo-enabled text message service
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For the curious: It's this Unicode character http://www.fileformat.info/info/unicode/char/2316/index.htm known as "Position Indicator" and it looks like a reticle. Kind of makes sense for a position-based service, but a bit hard to type :)
edit: Previous discussion about the actual icon for the app: http://news.ycombinator.com/item?id=4285919
They're very common and cheap; it's a single character domain name, not a single letter or number.
EDIT: Sorry, when I say "OP used [...]", I mean to say "OP was able to do it because of [...]". Punycode is handled by the browser, not done manually (except when registering the domain -- then you do it manually).
Only criticism would that the "accept request to share location" action button is labelled "share", which I initially glossed over, assuming that it meant "share to social network".
Of course, there isn't a single service that all of my friends use, apart from traditional SMS. Facebook Messenger comes closest, but I message people I am not Facebook friends with, so that's out.
I dream of a service that's like WhatsApp- platform agnostic, available to all- but also totally open with all the API access you'd need. Of course, I would imagine that is extremely difficult to get popular. Oh, and monetise.
Go to maps, press the arrow for current location, click the right arrow and you'll see the 'Share' button. One of the options is 'message'. It sends a google maps link.