I have had my samknows whitebox for about 2 years now - it just sits and runs tests every hour. No impact on performance.
Its reporting (internet page or via an Android app) is good. Useful for FTTC connection when modem stats are not available. Gives good latency and packet loss info "the right way round" with the tests run from the customer end of the line rather than by a remote server pinging the router.
Quietly impressed. Not sure what the use the data for - the don't really go into details.
BT Infinity 2 - IP profile 77 / 20 - super fast!
Previously BE Unlimited - 21,000 Download 1,200 Upload but then moved house - 6,500 Down, 1Mb/s up - gutted!
Ex <n>ildram , been to SKY MAX - 15,225 Download