  The warm Neptune GJ 3470b transits a nearby ($d=29$pc) bright slowly rotating
M1.5-dwarf star. Using spectroscopic observations during two transits with the
newly commissioned NEID spectrometer on the WIYN 3.5m Telescope at Kitt Peak
Observatory, we model the classical Rossiter-Mclaughlin effect yielding a
sky-projected obliquity of $\lambda=98_{-12}^{+15\:\circ}$ and a $v \sin i =
0.85_{-0.33}^{+0.27}$km/s. Leveraging information about the rotation period and
size of the host star, our analysis yields a true obliquity of
$\psi=95_{-8}^{+9\:\circ}$, revealing that GJ 3470b is on a polar orbit. Using
radial velocities from HIRES, HARPS and the Habitable-zone Planet Finder, we
show that the data are compatible with a long-term RV slope of $\dot{\gamma} =
-0.0022 \pm 0.0011$m/s/day over a baseline of 12.9 years. If the RV slope is
due to acceleration from another companion in the system, we show that such a
companion is capable of explaining the polar and mildly eccentric orbit of GJ
3470b using two different secular excitation models. The existence of an outer
companion can be further constrained with additional RV observations, Gaia
astrometry, and future high-contrast imaging observations. Lastly, we show that
tidal heating from GJ 3470b's mild eccentricity has most likely inflated the
radius of GJ 3470b by a factor of $\sim$1.5-1.7, which could help account for
its evaporating atmosphere.
