I wrote a simple service like this one: http://smarden.org/runit/runscripts.html#apache2
$ cat start_node_exporter
#!/data/data/com.termux/files/usr/bin/sh
termux-wake-lock
. $PREFIX/etc/profile
/data/data/com.termux/files/home/bin/node_exporter --collector.wifi --collector.tcpstat --collector.runit --collector.processes --collector.mountstats
I would like it to run on phone reboot