Modern Vespa

Someone should make an app where you can connect to a black box via blue tooth connected to your motor and electrical system to give you speedo, tacho, cht, and anything else you want without needing extra equipment such as a sip speedo. This way, you wouldn't have to replace your vintage equipment. Any programmers out there?

I actually built this a while back using a raspberry pi. It's far from just a black box. It's hardware engineering to get the sensors feeding in, which was a LOT of work. I was also streaming telemetry to a time series database in AWS for analytics.

If I resurrected the project, I'd probably use an Arduino because it recovers better from power dropouts.

If you want to catch up on what was involved, check out The Ves-pi project

I love it. Can I add that the same black box should also determine low PSI on the tires? That's a plus. And it'd save plenty of threads if the app could identify where the oil is coming from.

Do you mean a black box that is wired to the original wire harness and then wirelessly connects to your phone?
How do you want to display the information?
Do you have a budget in mind?

For full dash and electrical systems look to the Rally industry. But those tend to have four to five digits in the price.
There is a Raspberry Pi "dashboard" that functions nicely to display information on a tablet.
Many years ago there was the "Scooterputer", while interesting project on its own it was not for engine parameters etc.

Basically any info that the sip tacho indicates but is available via iphone app so that the the original speedo doesn't need to be replaced.