The Sig Gen capabilities in SoundMeter are a very nice bonus in an already excellent app.
I have a couple of suggestions for enhancements:
Frequency of sinusoidal tone.
It would be great to have an option for the frequency slider to step the frequency in discrete 1/3-octave intervals. The frequency points should be exact 1/3-octave band centre frequencies, e.g. 251.2 Hz rather than 250 Hz.
[Another option might be for musical intervals based on A = 440 Hz, although this wouldn't be of particular interest to me.]
Delete the label 'Type:'. It's (pretty much) obvious what the buttons do.
Maybe set the resolution of the slider range limits to 1 Hz rather than 0.001 Hz? I would tend to have the slider range set rather wide (e.g. 125 Hz to several kHz), although I can see that others might want extremely fine resolution.
Would be nice to have square wave and other noise colours (and band limits on the noise), but I think that the current Sig Gen capabilities are already pretty nice for a sound level meter app!