Strava

Yeah dude. On the graph on the main page just click on "heart rate" at the bottom and itll come up

There's no average HR there so the "on" clicky is disabled. I guess Strava doesn't like the format that GTC exports to:-

<trkpt lat="x.xxxxxxx" lon="x.xxxxxxx">
<ele>24.6510010</ele>
<time>2014-09-17T11:38:39Z</time>
<extensions>
<tp1:TrackPointExtension>
<tp1:hr>175</tp1:hr>
</tp1:TrackPointExtension>
</extensions>
</trkpt>

I'll have a snoop for other gpx formats that Strava will take HR data from.