The present invention provides for devices and methods for providing endovascular therapy, including facilitating establishment of vascular access, placement of endovascular sheaths, catheter tip localization, and administration of vascular occlusion. The invention includes a vessel cannulation device, an expandable sheath, an occlusion catheter, and a localizer each of which may be provided separately or used as part of a system. One embodiment of the invention is a vessel cannulation device including: a housing having a distal end with a distal tip and a proximal end； a guidewire lumen passing through the housing and at least the distal tip； a sensor coupled to the guidewire lumen； and an advancing member, which is configured for advancing at least one of a guidewire or a sheath and which is operably coupled to the sensor.
