I think it is quite close to "ultimate" application of tiny ATtiny10. Eventually two applications, frequency counter and digital volt meter is combined in just one code and its function can be switched by pushing switch ON or OFF as initial condition.

Here is the schematic. Still super simple and just added one switch for PB2. Indeed PB2 is working as (1) function selector, (2) frequency counter input, and (3) DVM meter input. Surely we can buy very high precision DVM and frequency counter but I'm myself a bit surprised to see my realisation just 50 cents SOT23-6 MCU. (The above schematic contains some unmounted components, for example IN4148 protection diode...)

And my assembly code eventually ( already released at github) approaches to the limit of ATtiny10, 1024 bytes (1 kB)....

Segment   Begin    End      Code   Data   Used    Size   Use%
---------------------------------------------------------------
[.cseg] 0x000000 0x0003ae    942      0    942    1024  92.0%
[.dseg] 0x000040 0x000060      0      0      0      32   0.0%
[.eseg] 0x000000 0x000000      0      0      0       0      -

Again it is dirty and not well organised but surely working as multi-function instrument. Actual operation can be found in the following movie... Have fun!!