collection.py

...
#GPX 	GPX 	Yes 	Yes 	Yes (read support needs libexpat)
    ("GPX", "raw"),
...

interpreter.py

>>> import fiona
>>> fiona.listlayers('docs/data/fells_loop.gpx')
[u'waypoints', u'routes', u'tracks', u'route_points', u'track_points']
>>> with fiona.open('docs/data/fells_loop.gpx', layer='routes') as routes:
...     print routes.schema
...
{'geometry': 'LineString', 'properties': OrderedDict([(u'name', 'str'), (u'cmt', 'str'), (u'desc', 'str'), (u'src', 'str'), (u'link1_href', 'str'), (u'link1_text', 'str'), (u'link1_type', 'str'), (u'link2_href', 'str'), (u'link2_text', 'str'), (u'link2_type', 'str'), (u'number', 'int'), (u'type', 'str')])}

Awesome.