Depends on the system you go with. Blitz R-VIT DS does not require additional sensors to read from AF from OBD2. HKS Camp 2 does.
What I do, like mentioned above, is read AF via OBD2 using DashCommand installed on a CarPC and keep a standalone AFR gauge on the glove box.
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2011 Twin Turbo PW nismo #113 - My Journal - My TT Build Thread
[ GTM GTX Stg2 TT || HKS EVC6 || Custom CarPC || F.I 3'' TDX CBE || SB 6puck clutch/ZSpeed CSC || BC BR Coilovers || SPC camber arms || Work VSS-X || Custom Headlights || PW:JDM CF Covers || Seibon CF Engine Cover ]
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