The iPhone's M7 processor (specifically its step counting): any way at all to calibrate it?

I find its step counting is extremely accurate when I’m walking outside in sneakers, but wildly inaccurate (often counts less than 50% of the steps) when I’m walking indoors even if it’s across long spaces like halls – and whether I’m barefoot or wearing soft shoes. Since sometimes much of my walking is indoors, and having a pedometer is such a great tool to inspire me to walk more, I would love to find any way to improve this. Is there any app that lets you have an effect on its calibration? (now I am just viewing its data with a simple display/pedometer app).