Tennis sensors keep dying. The hardware is never the problem.

On 1 March 2021 Babolat put it in writing: "we have stopped all sales of Babolat tennis connected devices." The rackets people had already bought kept working fine. The service behind them did not.

Babolat was not alone. HEAD, Sony and Zepp all wound their tennis sensor lines down over the same stretch, and the app partner behind Babolat's POP shut its doors as well. I have found exactly one source for those, and it sells a competing product, so I am not going to print dates I cannot stand behind. The pattern is not in dispute: the sensor was a client, the server was the product, and when the server went, so did the thing you bought.

I am building a tennis impact sensor that cannot fail that way. It talks to your phone over BLE, the protocol is documented, and there is no account to log into and no service to shut down. I have spent 18 years as an embedded engineer, mostly on boards that have to keep running long after anyone is watching them.

Where it actually is

Boards are at the fab. There is no finished product, no price, and no date. The next real milestone is a bench test that decides whether the signal survives the actual form factor, and that test has not happened yet.

What I keep to myself: how the sensing works, and the business numbers. I intend to sell this. Everything about the process, the tooling and the judgment calls is public in the build log.

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