There is no such thing as a one way link exchange. Either a link is exchanged or not.
What you might be missing is this simple fact:
If you open yourself up to allowing link exchange requests to come in to you either via the service you mentioned above or your own suggest link form, the other potential link partner now sees you are interested in linking with relevant like minded sites and he/she is more willing to link to you first (a one way link) - because the one initiating the link request almost always links first. You can then either use the service you mentioned above to verify a true linkback and also look at other useful metrics to help make your decision, or you can do that work manually. However you do it, you then choose to either leave the one way link as a one way, or you link back to it making it a link exchange.
There is alot of psychology involved with all of this. The important thing to take away are these four simple concepts:
- If you publish a suggest link form (using the service you mentioned above or manually), you let the world know you are open to linking and then your inbound link request activity jumps up. Yes some of it will be junk. Delete it and move on. You will get some good link requests especially if your own links are well categorized including categories that naturally attract the low hanging fruit from genres you would be open to link with.
- Potential link partners who suggest a link with you are more likely to go ahead and link to you because they are anticipating the link back. Sometimes they will link to you and forget about it hoping you will link to them in the future. This happens more often than not.
- You should always maintain full control over who you link back to (maintain high relvancy ALWAYS). If you get 30 link requests in a month and 8 of then go ahead and link to you and you only link back to 3 of them, then you got 5 one ways and 3 link exchanges in that month.
- Editorially earned links whether one way or via link exchange survive for a long time on the web. Paid links and other schemes don't last forever because the paid ones are set to auto expire making you have to pay more. Links obtained via blogs have the shortest life span.
A few final notes:
Many seo self proclaimed experts spout comments such as "link exchange is dead". Nothing could be further from the truth. It might be dead for them because they want you to spend thousands a month so they can optimize a few keywords for you every month. But the truth is that relevant link exchange is alive and well especially among niche industries such as the wedding industry. Editorally earned links (even from links pages) are crawled and counted by G (the proof is in your log reports) and are factored into rankings. G intentionally doesn't admit this or publish every links page on the planet in their index because by hiding some of what they don't want you do know, they help keep webmasters from abusing some of these methods.
G has never said "do not link exchange" and why would they? They want you to obtain links with editorial discretion. It helps them determine what is popular and what is not. They realize its normal for relevant sites to link to each other. They simply want you to avoid doing it excessively (avoid full duplex services offering hundreds of links every day). It's not normal for a typical ecommerce website to obtain a high number of links over a short period of time unless you have published a cure for cancer or if you are giving away free money.
The proof of what I am saying is in the index. Millions of websites with relevant links or resources pages rank in the top ten for their keywords.