I have been in a similar position as, like you, I find it easier to do stuff when someone else is expecting me to do it. In the absence of a co-founder, one of my strategies has been to create that sense of expectation by outsourcing parts of the work which then requires work from me to provide the outsourced person with what they need to do their bit.
On one recent project, I got going by knocking out a rough plan in Pivotal Tracker and then doing some pair programming on some portions of the code with someone I hired on oDesk. Having booked someone for a couple of hours a day for a week or two meant that I got started, and by using them only for small portions of the functionality meant that it didn't cost too much and I was motivated to get the other bits done myself that were dependencies for the next bit of functionality I was going to be working on with my pair programmer.
On one recent project, I got going by knocking out a rough plan in Pivotal Tracker and then doing some pair programming on some portions of the code with someone I hired on oDesk. Having booked someone for a couple of hours a day for a week or two meant that I got started, and by using them only for small portions of the functionality meant that it didn't cost too much and I was motivated to get the other bits done myself that were dependencies for the next bit of functionality I was going to be working on with my pair programmer.