Keep Close Friends: https://keepclosefriends.com
One day I noticed I was slowly losing touch with old friends - I moved, we all have busy lives and don't hang out just by chance any more. Those people used to be loved ones and now I wasn't sure. It felt like grief.
So I built a simple website where I can list relationships and ideal meeting frequency (say, 2-3 times a year), then get a few relationship stats and a reminder when it's time to reach out again.
I see it as a reminder that my life is short, and I like that. No other users yet but it feels right to try to help share that perspective around, for those who might want it.