For positive resolution, app needs to have these traits:

• Allows me to broadcast my location and willingness to hang on short notice (potential hangout starting in less than 30m)

• Allows me some choice over who I broadcast this to on a particular occasion (e.g. multiple circles)

• I use it for this purpose at least five times (e.g. Facebook could do the above, and I use it, but I don't want to for this purpose, so it doesn't count)

• I consider it successful at least twice (probably mostly based on 'does anyone show up?')