Sorry for resurrecting an old thread but for future reference someone developed a OBD-II mobile for megasquirt that will accept standard Bluetooth or WiFi dongles. Looks like their are DYI options but this looks easiest to me.
Original thread: http://www.miataturbo.net/ms-labs-miata-accessories-89 ...

Not sure if this is a bug but start speed currently jumps from 0mph to 19mph (30 kph) but 1 mph increments would be nice. Specifically, I would like to do a rolling start from 5mph to 60mph.

When reading the following article it seems there is some confusion about what data is overlayed on the map...

https://nasaspeed.news/toolshed-engineer/cheap-data-harrys-lap-timer/#comment-14

The author says the red/yellow/green overlay shows longitudinal and lateral g's. Unless I misunderstand ...

I'm running HLT 20.0.3 on my iPhone 6 and have been getting relatively stable connection with 3 iPhone4S's with MultiCam. Here's what I found worked best:
1. enable Bluetooth on all phones (seems like wifi needs to be off)
2. Start HLT on iPhone6, go to Timer -> Video and select the Internal Cam ...

Good point. An external GPS isn't even needed. Last I time checked, my iPhones internal GPS worked with HLT when I had the phone in airplane mode

I came up with a fix since I have a Dual XGPS160, which allows up to 5 iPhone connections. Instead of running MultiCam, I just installed HLT on each iPhone (they are all on the same iCloud Acct). After recording with the 'Multicams' I then (1) make note of the lap end times for each video, (2 ...

Bulls23, when you turned airplane mode off did your multicam device connect to a wifi network? I tried turning airplane mode off (with wifi off, Bluetooth on) and still no connection. If go into airplane mode with only wifi on, I get the multicam Bluetooth warning, but with both master and multicam ...

Interesting. My post above post was using a 4s in airplane mode with Bluetooth turned on. When I get home, I'll try turning airplane mode off, wifi off, and Bluetooth on and see if I get the same results.

Not sure if it's related, but airplane mode seemed to change in iOS9. You can be in airplane ...

I was just getting ready to post the same thing. I did some trouble shooting last night and found I could only get iOS multicam devices to connect with the master when they also had a wifi connection. I seem to remember they even connected over wifi with Bluetooth turned off. I could not get ...

Thanks for the spreadsheet and sorry for the late response. I got distracted trying to modify the data and get it back into HLT.

I was able to write a macro to change the speed, lateral-g, and lineal-g values; put the data back into a hlptrz file; even load the file back into HLT successfully; but ...