Eagle737
The 737 FCTM used to read “positive rate on the IVSI and Altimeter”
I believe that due to the sensitivity of the Instantaneous VSI this requirement was removed.
Using only the Altimeter, with its pressure lag, is a more conservative indication of positive rate. Particularly in a windshear encounter.
In a two crew aircraft both pilots are confirming positive rate before gear retraction giving redundancy.
“Positive rate” (Altimeter increasing) for gear retraction is therefore the same for Take Off or a Go Around.
The IVSI, RA, Ground flight relay, Attitude and external visual indications are all useful for your situational awareness, however all have limitations.